day15 p2 performance

Getting rid of the temp neighbor vector allocation is major speedup

day15/input.txt

@@ -0,0 +1,100 @@
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day15/part1.jl

@@ -0,0 +1,192 @@
+#!/usr/bin/env julia
+
+#=
+--- Day 15: Chiton ---
+
+You've almost reached the exit of the cave, but the walls are getting closer together. Your submarine can barely still fit, though; the main problem is that the walls of the cave are covered in chitons, and it would be best not to bump any of them.
+
+The cavern is large, but has a very low ceiling, restricting your motion to two dimensions. The shape of the cavern resembles a square; a quick scan of chiton density produces a map of risk level throughout the cave (your puzzle input). For example:
+
+1163751742
+1381373672
+2136511328
+3694931569
+7463417111
+1319128137
+1359912421
+3125421639
+1293138521
+2311944581
+
+You start in the top left position, your destination is the bottom right position, and you cannot move diagonally. The number at each position is its risk level; to determine the total risk of an entire path, add up the risk levels of each position you enter (that is, don't count the risk level of your starting position unless you enter it; leaving it adds no risk to your total).
+
+Your goal is to find a path with the lowest total risk. In this example, a path with the lowest total risk is highlighted here:
+
+1163751742
+1381373672
+2136511328
+3694931569
+7463417111
+1319128137
+1359912421
+3125421639
+1293138521
+2311944581
+
+The total risk of this path is 40 (the starting position is never entered, so its risk is not counted).
+
+What is the lowest total risk of any path from the top left to the bottom right?
+=#
+
+infile = length(ARGS) > 0 ? ARGS[1] : "input.txt"
+println("infile = ", infile)
+
+risk_map = reduce(vcat, [parse.(Int, split(line, ""))'
+                  for line in  eachline(infile)])
+
+function least_risk(E)
+    nrows, ncols = size(E)
+    row = nrows
+    col = ncols
+    cost = 0
+    path = zeros(Int, size(E))
+    while row > 1 || col > 1
+        cost += E[row, col]
+        path[row, col] = 1
+        if col == 1
+            row -= 1
+        elseif row == 1
+            col -= 1
+        else
+            if E[row, col-1] < E[row-1, col]
+                col -= 1
+            else
+                row -= 1
+            end
+        end
+    end
+    return cost, path
+end
+
+function neighbor_idx(nrows, ncols, y, x)
+    v = CartesianIndex[]
+    if x > 1
+        push!(v, CartesianIndex(y, x-1))
+    end
+    if x < ncols
+        push!(v, CartesianIndex(y, x+1))
+    end
+    if y > 1
+        push!(v, CartesianIndex(y-1, x))
+    end
+    if y < nrows
+        push!(v, CartesianIndex(y+1, x))
+    end
+    return v
+end
+
+function get_costs(R)
+    costs = zeros(Int, size(R))
+    dirs = zeros(Int, size(R))
+    nrows, ncols = size(R)
+    for col in 2:ncols
+        costs[1, col] = costs[1, col-1] + R[1, col]
+    end
+    for row in 2:nrows
+        costs[row, 1] = costs[row-1, 1] + R[row, 1]
+        for col in 2:ncols
+            if costs[row-1, col] < costs[row, col-1]
+                dirs[row, col] = 1
+                costs[row, col] = costs[row-1, col] + R[row, col]
+            else
+                costs[row, col] = costs[row, col-1] + R[row, col]
+            end
+        end
+    end
+
+    if false
+    # more passes
+    for i in 1:max(nrows, ncols)
+        for col in ncols-1:-1:1
+            rcost = costs[end, col+1] + R[end, col]
+            if rcost < costs[end, col]
+                costs[end, col] = rcost
+            end
+        end
+        for row in nrows-1:-1:1
+            dcost = costs[row+1, end] + R[row, end]
+            if dcost < costs[row, end]
+                costs[row, end] = dcost
+            end
+            for col in ncols-1:-1:1
+                rcost = costs[row, col+1] + R[row, col]
+                if rcost < costs[row, col]
+                    costs[row, col] = rcost
+                end
+                dcost = costs[row+1, col] + R[row, col]
+                if dcost < costs[row, col]
+                    costs[row, col] = dcost
+                end
+            end
+        end
+    end
+    end
+
+    for row in nrows:-1:1
+        for col in ncols:-1:1
+            idx = neighbor_idx(nrows, ncols, row, col)
+            c = minimum(costs[i] for i in idx) + R[row, col]
+            if c < costs[row, col]
+                costs[row, col] = c
+            end
+        end
+    end
+
+    for row in nrows:-1:1
+        for col in 1:ncols
+            idx = neighbor_idx(nrows, ncols, row, col)
+            c = minimum(costs[i] for i in idx) + R[row, col]
+            if c < costs[row, col]
+                costs[row, col] = c
+            end
+        end
+    end
+
+    for row in 1:nrows
+        for col in ncols:-1:1
+            idx = neighbor_idx(nrows, ncols, row, col)
+            c = minimum(costs[i] for i in idx) + R[row, col]
+            if c < costs[row, col]
+                costs[row, col] = c
+            end
+        end
+    end
+
+    for row in 1:nrows
+        for col in 1:ncols
+            idx = neighbor_idx(nrows, ncols, row, col)
+            c = minimum(costs[i] for i in idx) + R[row, col]
+            if c < costs[row, col]
+                costs[row, col] = c
+            end
+        end
+    end
+
+    return costs, dirs
+end
+
+#=
+cost, path = least_risk(risk_map)
+
+display(path)
+println()
+
+println("cost = ", cost)
+=#
+
+costs, dirs = get_costs(risk_map)
+
+display(costs)
+println()
+
+println("cost = ", costs[end, end])

day15/part2.jl

@@ -0,0 +1,240 @@
+#!/usr/bin/env julia
+
+#=
+--- Part Two ---
+
+Now that you know how to find low-risk paths in the cave, you can try to find your way out.
+
+The entire cave is actually five times larger in both dimensions than you thought; the area you originally scanned is just one tile in a 5x5 tile area that forms the full map. Your original map tile repeats to the right and downward; each time the tile repeats to the right or downward, all of its risk levels are 1 higher than the tile immediately up or left of it. However, risk levels above 9 wrap back around to 1. So, if your original map had some position with a risk level of 8, then that same position on each of the 25 total tiles would be as follows:
+
+8 9 1 2 3
+9 1 2 3 4
+1 2 3 4 5
+2 3 4 5 6
+3 4 5 6 7
+
+Each single digit above corresponds to the example position with a value of 8 on the top-left tile. Because the full map is actually five times larger in both dimensions, that position appears a total of 25 times, once in each duplicated tile, with the values shown above.
+
+Here is the full five-times-as-large version of the first example above, with the original map in the top left corner highlighted:
+
+11637517422274862853338597396444961841755517295286
+13813736722492484783351359589446246169155735727126
+21365113283247622439435873354154698446526571955763
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+75698651748671976285978218739618932984172914319528
+56475739656758684176786979528789718163989182927419
+67554889357866599146897761125791887223681299833479
+
+Equipped with the full map, you can now find a path from the top left corner to the bottom right corner with the lowest total risk:
+
+11637517422274862853338597396444961841755517295286
+13813736722492484783351359589446246169155735727126
+21365113283247622439435873354154698446526571955763
+36949315694715142671582625378269373648937148475914
+74634171118574528222968563933317967414442817852555
+13191281372421239248353234135946434524615754563572
+13599124212461123532357223464346833457545794456865
+31254216394236532741534764385264587549637569865174
+12931385212314249632342535174345364628545647573965
+23119445813422155692453326671356443778246755488935
+22748628533385973964449618417555172952866628316397
+24924847833513595894462461691557357271266846838237
+32476224394358733541546984465265719557637682166874
+47151426715826253782693736489371484759148259586125
+85745282229685639333179674144428178525553928963666
+24212392483532341359464345246157545635726865674683
+24611235323572234643468334575457944568656815567976
+42365327415347643852645875496375698651748671976285
+23142496323425351743453646285456475739656758684176
+34221556924533266713564437782467554889357866599146
+33859739644496184175551729528666283163977739427418
+35135958944624616915573572712668468382377957949348
+43587335415469844652657195576376821668748793277985
+58262537826937364893714847591482595861259361697236
+96856393331796741444281785255539289636664139174777
+35323413594643452461575456357268656746837976785794
+35722346434683345754579445686568155679767926678187
+53476438526458754963756986517486719762859782187396
+34253517434536462854564757396567586841767869795287
+45332667135644377824675548893578665991468977611257
+44961841755517295286662831639777394274188841538529
+46246169155735727126684683823779579493488168151459
+54698446526571955763768216687487932779859814388196
+69373648937148475914825958612593616972361472718347
+17967414442817852555392896366641391747775241285888
+46434524615754563572686567468379767857948187896815
+46833457545794456865681556797679266781878137789298
+64587549637569865174867197628597821873961893298417
+45364628545647573965675868417678697952878971816398
+56443778246755488935786659914689776112579188722368
+55172952866628316397773942741888415385299952649631
+57357271266846838237795794934881681514599279262561
+65719557637682166874879327798598143881961925499217
+71484759148259586125936169723614727183472583829458
+28178525553928963666413917477752412858886352396999
+57545635726865674683797678579481878968159298917926
+57944568656815567976792667818781377892989248891319
+75698651748671976285978218739618932984172914319528
+56475739656758684176786979528789718163989182927419
+67554889357866599146897761125791887223681299833479
+
+The total risk of this path is 315 (the starting position is still never entered, so its risk is not counted).
+
+Using the full map, what is the lowest total risk of any path from the top left to the bottom right?
+=#
+
+infile = length(ARGS) > 0 ? ARGS[1] : "input.txt"
+println("infile = ", infile)
+
+risk_map = reduce(vcat, [parse.(Int, split(line, ""))'
+                  for line in  eachline(infile)])
+
+function tile_map(R)
+    R2 = Matrix{eltype(R)}(undef, size(R) .* 5)
+    nrows, ncols = size(R)
+    for tile_row in 0:4
+        for tile_col in 0:4
+            add = tile_row + tile_col
+            rowstart = 1 + tile_row*nrows
+            rowend   = rowstart + nrows - 1
+            colstart = 1 + tile_col*ncols
+            colend   = colstart + ncols - 1
+            R2[rowstart:rowend, colstart:colend] = mod.(R .+ add .- 1, 9) .+ 1
+        end
+    end
+    return R2
+end
+
+risk_map = tile_map(risk_map)
+
+#display(risk_map)
+#println()
+#exit()
+
+function relax(nrows, ncols, R, costs, row, col; first=false)
+    c1 = costs[row, col]
+    c = c1
+    if col > 1
+        c = min(c, costs[row, col-1] + R[row, col])
+    end
+    if col < ncols
+        c = min(c, costs[row, col+1] + R[row, col])
+    end
+    if row > 1
+        c = min(c, costs[row-1, col] + R[row, col])
+    end
+    if row < nrows
+        c = min(c, costs[row+1, col] + R[row, col])
+    end
+
+    if c < c1
+        costs[row, col] = c
+        return true
+    end
+
+    return false
+end
+
+function relax_all(nrows, ncols, R, costs)
+    relaxed = false
+    for row in 1:nrows
+        for col in 1:ncols
+            v_relaxed = relax(nrows, ncols, R, costs, row, col)
+            relaxed = relaxed || v_relaxed
+        end
+    end
+    return relaxed
+end
+
+function get_costs(R)
+    costs = zeros(Int, size(R))
+    dirs = zeros(Int, size(R))
+    nrows, ncols = size(R)
+
+    # first pass, unconditional update looking only right/down. Avoids
+    # having to add an infinity value
+    costs[1,1] = 0
+    for col in 2:ncols
+        costs[1, col] = costs[1, col-1] + R[1, col]
+    end
+    for row in 2:nrows
+        costs[row, 1] = costs[row-1, 1] + R[row, 1]
+        for col in 2:ncols
+            if costs[row-1, col] < costs[row, col-1]
+                dirs[row, col] = 1
+                costs[row, col] = costs[row-1, col] + R[row, col]
+            else
+                costs[row, col] = costs[row, col-1] + R[row, col]
+            end
+        end
+    end
+
+    edges = ( (nrows-2)*(ncols-2)*4
+             +(nrows+ncols-4)*3
+             +4*2 )
+    max_passes = (nrows*ncols - 1) * edges
+
+    i = 1
+    while i <= max_passes
+        relaxed = relax_all(nrows, ncols, R, costs)
+        if !relaxed
+            break
+        end
+        i += 1
+    end
+    println("passes ", i)
+
+    return costs, dirs
+end
+
+@time costs, dirs = get_costs(risk_map)
+
+if length(costs) < 1000
+    display(costs)
+    println()
+end
+
+println("cost = ", costs[end, end])

day15/test.txt

@@ -0,0 +1,10 @@
+1163751742
+1381373672
+2136511328
+3694931569
+7463417111
+1319128137
+1359912421
+3125421639
+1293138521
+2311944581

day15/test2.txt

@@ -0,0 +1,50 @@
+11637517422274862853338597396444961841755517295286
+13813736722492484783351359589446246169155735727126
+21365113283247622439435873354154698446526571955763
+36949315694715142671582625378269373648937148475914
+74634171118574528222968563933317967414442817852555
+13191281372421239248353234135946434524615754563572
+13599124212461123532357223464346833457545794456865
+31254216394236532741534764385264587549637569865174
+12931385212314249632342535174345364628545647573965
+23119445813422155692453326671356443778246755488935
+22748628533385973964449618417555172952866628316397
+24924847833513595894462461691557357271266846838237
+32476224394358733541546984465265719557637682166874
+47151426715826253782693736489371484759148259586125
+85745282229685639333179674144428178525553928963666
+24212392483532341359464345246157545635726865674683
+24611235323572234643468334575457944568656815567976
+42365327415347643852645875496375698651748671976285
+23142496323425351743453646285456475739656758684176
+34221556924533266713564437782467554889357866599146
+33859739644496184175551729528666283163977739427418
+35135958944624616915573572712668468382377957949348
+43587335415469844652657195576376821668748793277985
+58262537826937364893714847591482595861259361697236
+96856393331796741444281785255539289636664139174777
+35323413594643452461575456357268656746837976785794
+35722346434683345754579445686568155679767926678187
+53476438526458754963756986517486719762859782187396
+34253517434536462854564757396567586841767869795287
+45332667135644377824675548893578665991468977611257
+44961841755517295286662831639777394274188841538529
+46246169155735727126684683823779579493488168151459
+54698446526571955763768216687487932779859814388196
+69373648937148475914825958612593616972361472718347
+17967414442817852555392896366641391747775241285888
+46434524615754563572686567468379767857948187896815
+46833457545794456865681556797679266781878137789298
+64587549637569865174867197628597821873961893298417
+45364628545647573965675868417678697952878971816398
+56443778246755488935786659914689776112579188722368
+55172952866628316397773942741888415385299952649631
+57357271266846838237795794934881681514599279262561
+65719557637682166874879327798598143881961925499217
+71484759148259586125936169723614727183472583829458
+28178525553928963666413917477752412858886352396999
+57545635726865674683797678579481878968159298917926
+57944568656815567976792667818781377892989248891319
+75698651748671976285978218739618932984172914319528
+56475739656758684176786979528789718163989182927419
+67554889357866599146897761125791887223681299833479

day15/test_snake.txt

@@ -0,0 +1,4 @@
+19111
+19191
+11191
+99991

day15/test_snake2.txt

@@ -0,0 +1,5 @@
+11199
+99199
+11199
+19999
+11111

day7.jl

@@ -0,0 +1,110 @@
+#!/usr/bin/env julia
+
+#=
+--- Day 7: The Treachery of Whales ---
+
+A giant whale has decided your submarine is its next meal, and it's much faster than you are. There's nowhere to run!
+
+Suddenly, a swarm of crabs (each in its own tiny submarine - it's too deep for them otherwise) zooms in to rescue you! They seem to be preparing to blast a hole in the ocean floor; sensors indicate a massive underground cave system just beyond where they're aiming!
+
+The crab submarines all need to be aligned before they'll have enough power to blast a large enough hole for your submarine to get through. However, it doesn't look like they'll be aligned before the whale catches you! Maybe you can help?
+
+There's one major catch - crab submarines can only move horizontally.
+
+You quickly make a list of the horizontal position of each crab (your puzzle input). Crab submarines have limited fuel, so you need to find a way to make all of their horizontal positions match while requiring them to spend as little fuel as possible.
+
+For example, consider the following horizontal positions:
+
+16,1,2,0,4,2,7,1,2,14
+
+This means there's a crab with horizontal position 16, a crab with horizontal position 1, and so on.
+
+Each change of 1 step in horizontal position of a single crab costs 1 fuel. You could choose any horizontal position to align them all on, but the one that costs the least fuel is horizontal position 2:
+
+    Move from 16 to 2: 14 fuel
+    Move from 1 to 2: 1 fuel
+    Move from 2 to 2: 0 fuel
+    Move from 0 to 2: 2 fuel
+    Move from 4 to 2: 2 fuel
+    Move from 2 to 2: 0 fuel
+    Move from 7 to 2: 5 fuel
+    Move from 1 to 2: 1 fuel
+    Move from 2 to 2: 0 fuel
+    Move from 14 to 2: 12 fuel
+
+This costs a total of 37 fuel. This is the cheapest possible outcome; more expensive outcomes include aligning at position 1 (41 fuel), position 3 (39 fuel), or position 10 (71 fuel).
+
+Determine the horizontal position that the crabs can align to using the least fuel possible. How much fuel must they spend to align to that position?
+
+--- Part Two ---
+
+The crabs don't seem interested in your proposed solution. Perhaps you misunderstand crab engineering?
+
+As it turns out, crab submarine engines don't burn fuel at a constant rate. Instead, each change of 1 step in horizontal position costs 1 more unit of fuel than the last: the first step costs 1, the second step costs 2, the third step costs 3, and so on.
+
+As each crab moves, moving further becomes more expensive. This changes the best horizontal position to align them all on; in the example above, this becomes 5:
+
+    Move from 16 to 5: 66 fuel
+    Move from 1 to 5: 10 fuel
+    Move from 2 to 5: 6 fuel
+    Move from 0 to 5: 15 fuel
+    Move from 4 to 5: 1 fuel
+    Move from 2 to 5: 6 fuel
+    Move from 7 to 5: 3 fuel
+    Move from 1 to 5: 10 fuel
+    Move from 2 to 5: 6 fuel
+    Move from 14 to 5: 45 fuel
+
+This costs a total of 168 fuel. This is the new cheapest possible outcome; the old alignment position (2) now costs 206 fuel instead.
+
+Determine the horizontal position that the crabs can align to using the least fuel possible so they can make you an escape route! How much fuel must they spend to align to that position?
+=# 
+
+using DelimitedFiles
+using Statistics
+
+infile = length(ARGS) > 0 ? ARGS[1] : "day7input.txt"
+println("infile = ", infile)
+
+hpos = vec(readdlm(infile, ',', Int))
+
+display(hpos)
+println()
+
+mean_hpos = mean(hpos)
+println(mean_hpos)
+
+center = round(Int, mean_hpos)
+
+function fuel_cost(crab_pos, align_pos)
+    return sum(abs.(crab_pos .- align_pos))
+end
+
+best = [-1, -1]
+for i in minimum(hpos):maximum(hpos)
+    cost = fuel_cost(hpos, i)
+    if best[1] == -1 || cost < best[1]
+        best[1] = cost
+        best[2] = i
+    end
+end
+
+println("center ", best[2])
+println("cost   ", best[1])
+
+function fuel_cost2(crab_pos, align_pos)
+    diffs = abs.(crab_pos .- align_pos)
+    return sum(diffs .* (diffs .+ 1) ./ 2)
+end
+
+best = [-1, -1]
+for i in minimum(hpos):maximum(hpos)
+    cost = fuel_cost2(hpos, i)
+    if best[1] == -1 || cost < best[1]
+        best[1] = cost
+        best[2] = i
+    end
+end
+
+println("center ", best[2])
+println("cost   ", best[1])

day7input.txt

@@ -0,0 +1 @@
+1101,1,29,67,1102,0,1,65,1008,65,35,66,1005,66,28,1,67,65,20,4,0,1001,65,1,65,1106,0,8,99,35,67,101,99,105,32,110,39,101,115,116,32,112,97,115,32,117,110,101,32,105,110,116,99,111,100,101,32,112,114,111,103,114,97,109,10,1425,266,740,842,335,1076,1125,108,728,131,553,757,316,361,475,1058,555,157,37,1501,287,61,22,394,886,535,235,734,1381,428,200,838,84,0,99,397,516,1260,1079,457,685,669,85,1161,851,1413,207,125,23,396,1024,637,712,942,320,507,32,686,1073,449,736,619,120,1092,674,769,519,26,42,366,187,261,389,583,170,700,695,531,57,263,1058,755,1215,413,201,617,311,443,694,285,677,722,1262,934,790,31,272,410,129,22,186,49,1040,399,19,624,132,1,35,515,423,1039,128,963,254,152,1306,33,360,484,463,483,254,741,284,14,155,6,16,1053,36,1299,637,985,470,476,383,717,304,31,209,263,70,1196,2,283,470,45,20,226,249,654,692,107,31,123,131,42,36,469,249,74,703,798,195,126,1699,135,143,1028,180,33,248,4,118,22,783,721,1033,1250,779,213,241,170,1026,0,124,709,672,349,286,494,134,361,938,985,539,267,240,951,496,431,449,242,804,422,24,202,76,947,414,396,681,142,366,342,256,978,373,677,1471,187,307,579,437,17,779,81,1380,241,69,61,758,1290,98,514,275,510,1427,185,139,816,1401,105,74,978,544,248,413,0,45,1107,223,332,723,745,71,70,330,727,261,1223,914,16,980,306,331,1011,132,70,1735,281,993,976,1,370,280,502,41,644,213,1191,518,464,693,446,44,930,1,23,1412,219,722,1028,84,552,1261,601,433,538,728,385,9,346,212,1017,7,80,88,336,480,1264,219,750,0,1080,711,1095,849,1270,175,20,314,452,620,1283,81,57,193,392,79,1330,220,396,184,922,921,902,199,56,107,32,67,275,91,202,49,4,312,372,262,49,172,493,1473,989,70,373,941,1116,798,709,865,105,442,555,1616,74,402,703,439,120,262,442,1704,1459,195,237,1763,376,734,28,867,370,6,1080,548,750,391,367,123,324,221,453,131,516,586,72,57,185,1667,468,439,225,1407,663,12,355,1320,595,60,59,158,279,365,670,505,14,240,1299,337,128,615,823,576,823,890,284,1196,717,955,1282,1002,20,176,32,222,33,248,634,885,703,543,368,585,1151,110,124,41,475,958,252,99,30,620,793,1021,540,154,635,1194,420,54,33,452,797,157,576,86,116,842,94,98,0,1162,38,483,138,949,316,1248,79,249,40,234,698,275,1239,573,649,815,348,48,78,1039,276,12,261,317,638,304,20,184,1152,711,1673,917,40,244,655,268,151,41,851,79,242,788,611,300,27,141,635,274,330,900,1023,498,269,267,46,436,844,1228,38,142,467,192,399,86,87,645,792,405,844,108,487,356,1251,332,146,128,383,1123,145,0,1148,688,127,316,579,15,215,293,73,1648,599,432,155,317,1054,205,155,451,1411,291,104,536,719,35,25,24,62,747,702,224,971,107,1210,114,41,472,29,286,4,920,0,197,135,112,308,191,1017,438,206,239,6,11,69,945,248,274,397,50,173,80,1349,268,585,590,1071,1127,351,929,106,989,396,209,691,17,149,1001,354,1296,473,179,152,141,1049,376,590,196,27,656,67,275,153,916,849,27,1093,73,156,30,1206,276,623,395,38,760,33,222,371,489,246,309,385,498,517,748,1384,1203,465,360,237,763,1173,94,431,48,770,491,132,564,84,472,1804,57,59,187,351,1340,265,1099,36,199,60,608,148,1209,1142,231,268,254,105,1020,200,1202,661,225,1313,55,808,770,80,522,185,129,36,476,815,1424,534,583,285,15,21,607,722,242,33,299,672,1253,1078,142,285,417,461,261,310,296,1934,271,144,1572,155,1039,881,1097,18,226,45,789,213,309,32,603,1102,5,81,511,672,314,7,1471,104,196,875,286,4,198,472,549,613,1453,139,596,270,164,417,709,437,27,86,758,1365,216,38,1047,124,96,255,72,67,1372,143,120,502,276,922,89,231,491,1330,245,473,25,944,266,1475,569,215,484,73,264,214,608,423,333,879,251,300,32,18,514,135,1349,80,493,569,784,2,794,846,596,30,862,318,207,546,551,1548,547,181,1219,354,650,791,53,20,629,52,105,98,312,140,111,1451,973,11,17,821,724,1836,376,82,248,86,730,1061,47,309,142,1039,114,157,26,307,1058,803,723,105,170,59,239,181,601,79,564,671,636,1465,530,533,75,261,1522,537,96,984,71,504,572,923,85,103,567,780,102,4,835,463,684,427,1091,1104,1163,626,1015,395,1881,43,490,906,1013,398,113,95,332,215,14,8,85,92,1579

day7test.txt

@@ -0,0 +1 @@
+16,1,2,0,4,2,7,1,2,14

day8/input.txt

@@ -0,0 +1,200 @@
+fgcae ebafc cabdef eg abecfg abgfed feg gafdc bceg ebgcadf | defagbc faecg cfdag gecb
+eagd cad fgadbc aefdcg dcebfg fcegd cbeaf ad dbgfeca defca | cfdeg gdcabf fcgde afgced
+gfdeca aeb eb fbdag eafdc adfbe cefdab bdaegcf efbc ecadgb | eb dbafe eab faecd
+facbdge efdg gcafd daegc caegb aecfdb ade ed gafbdc dgfeac | de abcdef faedcg dfgca
+dcaegbf bc dcgeab cbgad cebg cdfaeb fbadg acdge cefdga cdb | gdcfae gbec gdace cgadfe
+ceagfbd fbaeg fadge fbegad abgecf dafcg ed edab ged dfcbeg | gebfa de gbafec ed
+acedbf adfbg cgafedb geac cgb befcgd bcgaf bfgace cg bfeac | bcdfeg fecba cafgeb bgdfa
+egadc cea ac agbcedf cgab bgcade fbcaed eadfbg fegdc ebdag | fdecabg fcged cdbage efgdab
+cbfge gdc cdea efdag dc cdfeg gfbcad gcdeaf cdeagbf egfadb | dfcge egcfd fcdbag dc
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+bcafed defgcab fgcb cfbae cagde agebfc gbcae gbe gadefb gb | bg gfcaeb bg aedgc
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+eac fbdgec ea eadb cbaeg agfdecb eafdgc dcgbe bcfga adcbeg | aec abde eac ea
+cedb gcadbe ed edgfbac fbega abdge gacdb fdacgb dcefag aed | cdagb gbcafd gdefac gedafc
+cae agfbec ae begcd feab fadgbc ecfadg ecabg cdgbefa cabfg | ecgba afcgb efba dgeafc
+fecgabd badf efadg abedfg fea fdgceb fedgb aebfgc af gdcae | ebfgca fae fea af
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+edfga cgefda gcdbe fbae ab egdabf cfgbda deabg bad adefcgb | ebadg agdeb fbae gbdae
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+acefgd ebgaf egfda egcd bgfaecd dgcfa ed abcefd efd abdgcf | def ebgaf fed befcda
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+badgfc dg bagcde bceda dbcfea beafg debag adg fcbadeg edgc | gebda dcagbf dceba egfab
+edcf dacfbg dbcefag fbd df bdegfc ebdagc bgfea begcd bfedg | dgebc cbgde dgfbac bdf
+bdcfg acegfb acebfd fdcag egadcf da daf cgeaf edag bafcegd | gdcaf fgaec bafdec fdaecb
+cagefd fde gdfba fcgaedb abefd ef dafbeg ebfg afcbgd ebdca | egdbfa bceda dfabg bdace
+fcgb gcdae bg gfadeb cbfegd fcabed bdg gcdbe fdcbe adbefcg | dgb gfbdec befdc gfbc
+fabde bgfde bgecda cedgb gf cabfdeg ebfdgc fgbeac fcdg gfb | fgbde efdgb edgbc afedb
+ebacf cedfab fde eabfd fd baecgf bagde agdebfc dfcb egfadc | ebfdgac acdegf abdefc ebfad
+gdcb cd cfgae cgbedf fbegd efgdc fadcbe gfeacdb dce dfagbe | gbcd cde gacfe gefdbc
+geb afedgb bfegca bgade eg dgef gadbc eafdb afebdcg fcbead | cagbd defcba dbafec geafcb
+fgbdc gbfade gba gefa dbafg cbadge bfgecda ga edbafc dfabe | afbdeg dgfba bgdfa dcfgb
+agef badce ef febad cabfdg gdfab cbgeafd egfbdc defgba fbe | abefd geaf gafdbe ebcad
+gd gad bfdg gecba fedabcg fcgeda aedfbc adebf agbdfe dgeab | ebcdaf agd gcfbdae egacb
+cedbfa ba cgbfa abf dfegac cafeg gabe befgca ebdfcag cbfdg | fab aegcf faecbd fdcebga
+daefg febdga aegfdbc efgdca eafb bge eb agbdec febgd gbdfc | gbcfd edbfg egb bacegd
+fbdecg bdafec cfaeb gedac def dceaf abfd fd gfecba gfdaecb | ebfac bdfa gbcdef fd
+fcbga cbdfeag bafgce fdacg dc fcd fcgbad fadge efcdgb cdab | gaefcb bafegcd acdb abcgf
+ecgabd acgdf abge ae bcfead fgdaceb ead daegc bcdefg gcbed | egba gaecd cgadbe gdbce
+aegfbc gf afebdc agebdfc ebcdf feg dcefg bdfg dcgea bgedcf | edbfcg fdgb bdgafce febgcd
+dcg bcdefa dbfceg fdeacg acbeg bfeagcd cfdae dg dfag agdec | dfcgea dg egdca edagc
+agcfeb fagbed fdbceg bag gebfd afgd agbfcde acbed ag badeg | cbdea fcedgb gfebac abcegf
+adbegfc fgdace cadge afcg ebdfca ebgad eac bfgdce cgefd ca | acged fcedg ebagd dgacefb
+gfeadb gfeab bcfa agebcfd aebgfc fecgbd efc fc gadec egcfa | fgbace fc debgcf afgceb
+bacg ab cfgbd bfadge acfed fgdecb agedcbf fcabgd bfa dbafc | gfdcb cbga abcg afecbdg
+ge beagc cfgabd bgaced bgcda fbadgec age ecdagf egbd fcbae | aeg gedbac cadfeg fbgcda
+dgbafe abfdgec gdf fd agebcf gadec dfcgba befd edfga aebfg | abcgefd dagec dfg df
+edfcga bcegd baeg cbgdae agdbc gce acgdebf eg gfadbc cefbd | dcbeg bgedc cedbg edcbg
+adfbe dg cagef dfgb gdbeca aefdg gda edcbaf fdgeba gdecbfa | cdabef eafbd bafcegd dg
+cd edcbfg dbage fcaebdg facd bgcfea afbedc afbec dbc adecb | adegb bcefag abegd cbgedf
+gdcbf da ecgbfda adc adgb bagcfd dfbcea egfac dfbceg gdacf | gdba cfdbg adbfec fcaeg
+bcg bc gdcbae dbca abfgde gdeba ebfacdg egcba faceg dgfbce | geadb badecg ecbfgd baecg

day8/part1.jl

@@ -0,0 +1,92 @@
+#!/usr/bin/env julia
+
+#=
+--- Day 8: Seven Segment Search ---
+
+You barely reach the safety of the cave when the whale smashes into the cave mouth, collapsing it. Sensors indicate another exit to this cave at a much greater depth, so you have no choice but to press on.
+
+As your submarine slowly makes its way through the cave system, you notice that the four-digit seven-segment displays in your submarine are malfunctioning; they must have been damaged during the escape. You'll be in a lot of trouble without them, so you'd better figure out what's wrong.
+
+Each digit of a seven-segment display is rendered by turning on or off any of seven segments named a through g:
+
+  0:      1:      2:      3:      4:
+ aaaa    ....    aaaa    aaaa    ....
+b    c  .    c  .    c  .    c  b    c
+b    c  .    c  .    c  .    c  b    c
+ ....    ....    dddd    dddd    dddd
+e    f  .    f  e    .  .    f  .    f
+e    f  .    f  e    .  .    f  .    f
+ gggg    ....    gggg    gggg    ....
+
+  5:      6:      7:      8:      9:
+ aaaa    aaaa    aaaa    aaaa    aaaa
+b    .  b    .  .    c  b    c  b    c
+b    .  b    .  .    c  b    c  b    c
+ dddd    dddd    ....    dddd    dddd
+.    f  e    f  .    f  e    f  .    f
+.    f  e    f  .    f  e    f  .    f
+ gggg    gggg    ....    gggg    gggg
+
+So, to render a 1, only segments c and f would be turned on; the rest would be off. To render a 7, only segments a, c, and f would be turned on.
+
+The problem is that the signals which control the segments have been mixed up on each display. The submarine is still trying to display numbers by producing output on signal wires a through g, but those wires are connected to segments randomly. Worse, the wire/segment connections are mixed up separately for each four-digit display! (All of the digits within a display use the same connections, though.)
+
+So, you might know that only signal wires b and g are turned on, but that doesn't mean segments b and g are turned on: the only digit that uses two segments is 1, so it must mean segments c and f are meant to be on. With just that information, you still can't tell which wire (b/g) goes to which segment (c/f). For that, you'll need to collect more information.
+
+For each display, you watch the changing signals for a while, make a note of all ten unique signal patterns you see, and then write down a single four digit output value (your puzzle input). Using the signal patterns, you should be able to work out which pattern corresponds to which digit.
+
+For example, here is what you might see in a single entry in your notes:
+
+acedgfb cdfbe gcdfa fbcad dab cefabd cdfgeb eafb cagedb ab |
+cdfeb fcadb cdfeb cdbaf
+
+(The entry is wrapped here to two lines so it fits; in your notes, it will all be on a single line.)
+
+Each entry consists of ten unique signal patterns, a | delimiter, and finally the four digit output value. Within an entry, the same wire/segment connections are used (but you don't know what the connections actually are). The unique signal patterns correspond to the ten different ways the submarine tries to render a digit using the current wire/segment connections. Because 7 is the only digit that uses three segments, dab in the above example means that to render a 7, signal lines d, a, and b are on. Because 4 is the only digit that uses four segments, eafb means that to render a 4, signal lines e, a, f, and b are on.
+
+Using this information, you should be able to work out which combination of signal wires corresponds to each of the ten digits. Then, you can decode the four digit output value. Unfortunately, in the above example, all of the digits in the output value (cdfeb fcadb cdfeb cdbaf) use five segments and are more difficult to deduce.
+
+For now, focus on the easy digits. Consider this larger example:
+
+be cfbegad cbdgef fgaecd cgeb fdcge agebfd fecdb fabcd edb |
+fdgacbe cefdb cefbgd gcbe
+edbfga begcd cbg gc gcadebf fbgde acbgfd abcde gfcbed gfec |
+fcgedb cgb dgebacf gc
+fgaebd cg bdaec gdafb agbcfd gdcbef bgcad gfac gcb cdgabef |
+cg cg fdcagb cbg
+fbegcd cbd adcefb dageb afcb bc aefdc ecdab fgdeca fcdbega |
+efabcd cedba gadfec cb
+aecbfdg fbg gf bafeg dbefa fcge gcbea fcaegb dgceab fcbdga |
+gecf egdcabf bgf bfgea
+fgeab ca afcebg bdacfeg cfaedg gcfdb baec bfadeg bafgc acf |
+gebdcfa ecba ca fadegcb
+dbcfg fgd bdegcaf fgec aegbdf ecdfab fbedc dacgb gdcebf gf |
+cefg dcbef fcge gbcadfe
+bdfegc cbegaf gecbf dfcage bdacg ed bedf ced adcbefg gebcd |
+ed bcgafe cdgba cbgef
+egadfb cdbfeg cegd fecab cgb gbdefca cg fgcdab egfdb bfceg |
+gbdfcae bgc cg cgb
+gcafb gcf dcaebfg ecagb gf abcdeg gaef cafbge fdbac fegbdc |
+fgae cfgab fg bagce
+
+Because the digits 1, 4, 7, and 8 each use a unique number of segments, you should be able to tell which combinations of signals correspond to those digits. Counting only digits in the output values (the part after | on each line), in the above example, there are 26 instances of digits that use a unique number of segments (highlighted above).
+
+In the output values, how many times do digits 1, 4, 7, or 8 appear?
+=#
+
+infile = length(ARGS) > 0 ? ARGS[1] : "input.txt"
+println("infile = ", infile)
+
+unique_sizes = Set([2, 4, 3, 7])
+
+unique_size_output_count = 0
+
+for line in eachline(infile)
+    global unique_size_output_count
+    inputs, outputs = [split(v) for v in split(line, " | ")]
+    unique_idx = findall(s -> length(s) in unique_sizes, outputs)
+    println(outputs, unique_idx)
+    unique_size_output_count += length(unique_idx)
+end
+
+println("unique size output count ", unique_size_output_count)

day8/part2.jl

@@ -0,0 +1,152 @@
+#!/usr/bin/env julia
+
+#=
+--- Part Two ---
+
+Through a little deduction, you should now be able to determine the remaining digits. Consider again the first example above:
+
+acedgfb cdfbe gcdfa fbcad dab cefabd cdfgeb eafb cagedb ab |
+cdfeb fcadb cdfeb cdbaf
+
+After some careful analysis, the mapping between signal wires and segments only make sense in the following configuration:
+
+ dddd
+e    a
+e    a
+ ffff
+g    b
+g    b
+ cccc
+
+So, the unique signal patterns would correspond to the following digits:
+
+    acedgfb: 8
+    cdfbe: 5
+    gcdfa: 2
+    fbcad: 3
+    dab: 7
+    cefabd: 9
+    cdfgeb: 6
+    eafb: 4
+    cagedb: 0
+    ab: 1
+
+Then, the four digits of the output value can be decoded:
+
+    cdfeb: 5
+    fcadb: 3
+    cdfeb: 5
+    cdbaf: 3
+
+Therefore, the output value for this entry is 5353.
+
+Following this same process for each entry in the second, larger example above, the output value of each entry can be determined:
+
+    fdgacbe cefdb cefbgd gcbe: 8394
+    fcgedb cgb dgebacf gc: 9781
+    cg cg fdcagb cbg: 1197
+    efabcd cedba gadfec cb: 9361
+    gecf egdcabf bgf bfgea: 4873
+    gebdcfa ecba ca fadegcb: 8418
+    cefg dcbef fcge gbcadfe: 4548
+    ed bcgafe cdgba cbgef: 1625
+    gbdfcae bgc cg cgb: 8717
+    fgae cfgab fg bagce: 4315
+
+Adding all of the output values in this larger example produces 61229.
+
+For each entry, determine all of the wire/segment connections and decode the four-digit output values. What do you get if you add up all of the output values?
+=#
+
+infile = length(ARGS) > 0 ? ARGS[1] : "input.txt"
+println("infile = ", infile)
+
+function charset(s)
+    return Set(c for c in s)
+end
+
+unique_sizes = Set([2, 4, 3, 7])
+size_map = Dict(2 => [1],
+                3 => [7],
+                4 => [4],
+                5 => [2, 3, 5],
+                6 => [0, 6, 9],
+                7 => [8])
+
+segment_map = Dict(0 => "abcefg",
+                   1 => "cf",
+                   2 => "acdeg",
+                   3 => "acdfg",
+                   4 => "bcdf",
+                   5 => "abdfg",
+                   6 => "abdefg",
+                   7 => "acf",
+                   8 => "abcdefg",
+                   9 => "abcdfg")
+
+set_num_map = Dict(charset(v) => k for (k, v) in segment_map)
+
+function get_map(inputs)
+    segmap = Dict(c => charset("abcdefg") for c in charset("abcdefg"))
+    by_len = Dict{Int, Vector{Set{Char}}}()
+    for s in inputs
+        len = length(s)
+        if haskey(by_len, len)
+            push!(by_len[len], charset(s))
+        else
+            by_len[len] = [charset(s)]
+        end
+    end
+    # segment 'a' is the element in 7 and not 1
+    segmap['a'] = setdiff(by_len[3][1], by_len[2][1])
+
+    # segment 'f' is the element in 1 that is also in all
+    # of the len 6 numbers [0, 6, 9], and segment 'c' is the
+    # other element in 1
+    len6_intersect = intersect(by_len[6][1], by_len[6][2], by_len[6][3])
+    segmap['f'] = intersect(by_len[2][1], len6_intersect)
+    segmap['c'] = setdiff(by_len[2][1], segmap['f'])
+
+    # segment 'b' is the element in 4 other than c/f that is also in all of
+    # the len 6 numbers, and 'd' is the other one
+    segmap['b'] = intersect(setdiff(by_len[4][1], by_len[2][1]),
+                            len6_intersect)
+    segmap['d'] = setdiff(setdiff(by_len[4][1], by_len[2][1]),
+                          segmap['b'])
+
+    # segment 'g' is the element in all len 6 numbers that is not any that
+    # we have already found
+    segmap['g'] = setdiff(len6_intersect,
+                          union(segmap['a'], segmap['f'], segmap['c'],
+                                segmap['b'], segmap['d']))
+    segmap['e'] = setdiff(segmap['e'],
+                          union(segmap['a'], segmap['f'], segmap['c'],
+                                segmap['b'], segmap['d'], segmap['g']))
+
+    segs_to_num = Dict{Set{Char}, Int}()
+    for (num, segs) in segment_map
+        num_seg_set = Set{Char}()
+        for c in segs
+            union!(num_seg_set, segmap[c])
+        end
+        segs_to_num[num_seg_set] = num
+    end
+    return segs_to_num
+end
+
+total = 0
+
+for line in eachline(infile)
+    global total
+    inputs, outputs = [split(v) for v in split(line, " | ")]
+    set_to_num = get_map(inputs)
+    
+    v = 0
+    nout = length(outputs)
+    for (i, s) in enumerate(outputs)
+        v += set_to_num[charset(s)] * 10^(nout - i)
+    end
+    total += v
+end
+
+println("sum ", total)

day8/test.txt

@@ -0,0 +1,10 @@
+be cfbegad cbdgef fgaecd cgeb fdcge agebfd fecdb fabcd edb | fdgacbe cefdb cefbgd gcbe
+edbfga begcd cbg gc gcadebf fbgde acbgfd abcde gfcbed gfec | fcgedb cgb dgebacf gc
+fgaebd cg bdaec gdafb agbcfd gdcbef bgcad gfac gcb cdgabef | cg cg fdcagb cbg
+fbegcd cbd adcefb dageb afcb bc aefdc ecdab fgdeca fcdbega | efabcd cedba gadfec cb
+aecbfdg fbg gf bafeg dbefa fcge gcbea fcaegb dgceab fcbdga | gecf egdcabf bgf bfgea
+fgeab ca afcebg bdacfeg cfaedg gcfdb baec bfadeg bafgc acf | gebdcfa ecba ca fadegcb
+dbcfg fgd bdegcaf fgec aegbdf ecdfab fbedc dacgb gdcebf gf | cefg dcbef fcge gbcadfe
+bdfegc cbegaf gecbf dfcage bdacg ed bedf ced adcbefg gebcd | ed bcgafe cdgba cbgef
+egadfb cdbfeg cegd fecab cgb gbdefca cg fgcdab egfdb bfceg | gbdfcae bgc cg cgb
+gcafb gcf dcaebfg ecagb gf abcdeg gaef cafbge fdbac fegbdc | fgae cfgab fg bagce

day9/input.txt

@@ -0,0 +1,100 @@
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day9/part1.jl

@@ -0,0 +1,70 @@
+#!/usr/bin/env julia
+
+#=
+--- Day 9: Smoke Basin ---
+
+These caves seem to be lava tubes. Parts are even still volcanically active; small hydrothermal vents release smoke into the caves that slowly settles like rain.
+
+If you can model how the smoke flows through the caves, you might be able to avoid it and be that much safer. The submarine generates a heightmap of the floor of the nearby caves for you (your puzzle input).
+
+Smoke flows to the lowest point of the area it's in. For example, consider the following heightmap:
+
+2199943210
+3987894921
+9856789892
+8767896789
+9899965678
+
+Each number corresponds to the height of a particular location, where 9 is the highest and 0 is the lowest a location can be.
+
+Your first goal is to find the low points - the locations that are lower than any of its adjacent locations. Most locations have four adjacent locations (up, down, left, and right); locations on the edge or corner of the map have three or two adjacent locations, respectively. (Diagonal locations do not count as adjacent.)
+
+In the above example, there are four low points, all highlighted: two are in the first row (a 1 and a 0), one is in the third row (a 5), and one is in the bottom row (also a 5). All other locations on the heightmap have some lower adjacent location, and so are not low points.
+
+The risk level of a low point is 1 plus its height. In the above example, the risk levels of the low points are 2, 1, 6, and 6. The sum of the risk levels of all low points in the heightmap is therefore 15.
+
+Find all of the low points on your heightmap. What is the sum of the risk levels of all low points on your heightmap?
+=#
+
+infile = length(ARGS) > 0 ? ARGS[1] : "input.txt"
+println("infile = ", infile)
+
+depth_map = reduce(vcat, [parse.(Int, split(line, ""))'
+                          for line in  eachline(infile)])
+
+#display(depth_map)
+#println()
+
+
+function neighbors(m, y, x)
+    nrows, ncols = size(m)
+    v = eltype(m)[]
+    if x > 1
+        push!(v, m[y, x-1])
+    end
+    if x < ncols
+        push!(v, m[y, x+1])
+    end
+    if y > 1
+        push!(v, m[y-1, x])
+    end
+    if y < nrows
+        push!(v, m[y+1, x])
+    end
+    return v
+end
+
+function get_low_sum(m)
+    total = 0
+    nrows, ncols = size(m)
+    for x in 1:ncols
+        for y in 1:nrows
+            if all(m[y, x] .< neighbors(m, y, x))
+                total += m[y, x] + 1
+            end
+        end
+    end
+    return total
+end
+
+println(get_low_sum(depth_map))

day9/part2.jl

@@ -0,0 +1,146 @@
+#!/usr/bin/env julia
+
+#= --- Part Two ---
+
+Next, you need to find the largest basins so you know what areas are most important to avoid.
+
+A basin is all locations that eventually flow downward to a single low point. Therefore, every low point has a basin, although some basins are very small. Locations of height 9 do not count as being in any basin, and all other locations will always be part of exactly one basin.
+
+The size of a basin is the number of locations within the basin, including the low point. The example above has four basins.
+
+The top-left basin, size 3:
+
+2199943210
+3987894921
+9856789892
+8767896789
+9899965678
+
+The top-right basin, size 9:
+
+2199943210
+3987894921
+9856789892
+8767896789
+9899965678
+
+The middle basin, size 14:
+
+2199943210
+3987894921
+9856789892
+8767896789
+9899965678
+
+The bottom-right basin, size 9:
+
+2199943210
+3987894921
+9856789892
+8767896789
+9899965678
+
+Find the three largest basins and multiply their sizes together. In the above example, this is 9 * 14 * 9 = 1134.
+
+What do you get if you multiply together the sizes of the three largest basins?
+=#
+
+infile = length(ARGS) > 0 ? ARGS[1] : "input.txt"
+println("infile = ", infile)
+
+depth_map = reduce(vcat, [parse.(Int, split(line, ""))'
+                          for line in  eachline(infile)])
+
+function neighbor_idx(nrows, ncols, y, x)
+    v = CartesianIndex[]
+    if x > 1
+        push!(v, CartesianIndex(y, x-1))
+    end
+    if x < ncols
+        push!(v, CartesianIndex(y, x+1))
+    end
+    if y > 1
+        push!(v, CartesianIndex(y-1, x))
+    end
+    if y < nrows
+        push!(v, CartesianIndex(y+1, x))
+    end
+    return v
+end
+
+
+function neighbors(m, y, x)
+    nrows, ncols = size(m)
+    v = eltype(m)[]
+    if x > 1
+        push!(v, m[y, x-1])
+    end
+    if x < ncols
+        push!(v, m[y, x+1])
+    end
+    if y > 1
+        push!(v, m[y-1, x])
+    end
+    if y < nrows
+        push!(v, m[y+1, x])
+    end
+    return v
+end
+
+function flow_neighbors(m, y, x, flow_map, flow_count)
+    nrows, ncols = size(m)
+    nidx = neighbor_idx(nrows, ncols, y, x)
+    v = m[y, x]
+    if v == 9
+        flow_count[y, x] = 0
+        return
+    end
+    smallest_v = v
+    flow_idx = flow_map[y, x]
+    for idx in nidx
+        if m[idx] < smallest_v
+            smallest_v = m[idx]
+            flow_idx = flow_map[idx]
+            while flow_map[flow_idx] != flow_idx
+                flow_idx = flow_map[flow_idx]
+            end
+        end
+    end
+    if smallest_v != v
+        flow_count[flow_idx] += flow_count[y, x]
+        flow_count[y, x] = 0
+        flow_map[y, x] = flow_idx
+    end
+    #println(y, "x", x)
+    #display(flow_count)
+    #println()
+end
+
+function flow_all(m)
+    total = 0
+    nrows, ncols = size(m)
+    flow_count = ones(Int, nrows, ncols)
+    flow_map = reshape([CartesianIndex(y, x)
+                        for x in 1:ncols
+                        for y in 1:nrows], nrows, ncols)
+    for x in 1:ncols
+        for y in 1:nrows
+            flow_neighbors(m, y, x, flow_map, flow_count)
+        end
+    end
+    return flow_map, flow_count
+end
+
+map, count = flow_all(depth_map)
+
+if (length(depth_map) < 100)
+    display(count)
+    println()
+end
+
+basins = sort(filter(x -> x > 0, count))
+display(basins)
+println()
+
+println("nbasins = ", length(basins))
+println("largest_prod = ", prod(basins[end-2:end]))

day9/test.txt

@@ -0,0 +1,5 @@
+2199943210
+3987894921
+9856789892
+8767896789
+9899965678