add day8

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)