days 1-3

day1.jl

@@ -0,0 +1,20 @@
+using DelimitedFiles
+
+depths = readdlm("day1input.txt")
+
+diffs = depths[2:end] - depths[1:end-1]
+
+pos_diff_count = size(findall(diffs .> 0), 1)
+
+println("depth increases: ", pos_diff_count, " / ", size(diffs, 1))
+
+window_size = 3
+
+window_sums = [sum(depths[i:i+2]) for i in 1:size(depths, 1)-2]
+
+window_diffs = window_sums[2:end] - window_sums[1:end-1]
+
+pos_wdiff_count = size(findall(window_diffs .> 0), 1)
+
+println("window sum increases: ", pos_wdiff_count,
+        " / ", size(window_diffs, 1))

day2.jl

@@ -0,0 +1,46 @@
+using DelimitedFiles
+
+course = readdlm("day2input.txt")
+
+depth = 0
+horizontal = 0
+
+for row in 1:size(course, 1)
+    global horizontal, depth
+    direction = course[row, 1]
+    value = course[row, 2]
+    if direction == "forward"
+        horizontal += value
+    elseif direction == "up"
+        depth -= value
+    elseif direction == "down"
+        depth += value
+    end
+end
+
+println("depth = ", depth)
+println("horiz = ", horizontal)
+println("prod  = ", depth * horizontal)
+
+depth = 0
+horizontal = 0
+aim = 0
+
+for row in 1:size(course, 1)
+    global horizontal, depth, aim
+    direction = course[row, 1]
+    value = course[row, 2]
+    if direction == "forward"
+        horizontal += value
+        depth += value * aim
+    elseif direction == "up"
+        aim -= value
+    elseif direction == "down"
+        aim += value
+    end
+end
+
+println("depth = ", depth)
+println("horiz = ", horizontal)
+println("aim   = ", aim)
+println("prod  = ", depth * horizontal)

day3.jl

@@ -0,0 +1,68 @@
+using DelimitedFiles
+
+infile = size(ARGS, 1) > 0 ? ARGS[1] : "day3input.txt"
+println("infile = ", infile)
+
+diags = readdlm(infile, ' ', String)
+
+n = size(diags, 1)
+w = length(diags[1])
+
+half_n = n / 2
+
+gamma = 0
+epsilon = 0
+
+for i in 1:w
+    global gamma, epsilon
+    is_one_at_i(s) = s[i] == '1' ? true : false
+    one_count = size(findall(is_one_at_i, diags), 1)
+    v = 2^(w-i)
+    if one_count > half_n
+        gamma += v
+    else
+        epsilon += v
+    end
+end
+
+println("gamma   = ", gamma)
+println("epsilon = ", epsilon)
+println("prod    = ", gamma * epsilon)
+
+o2gen = view(diags, :)
+co2scrub = view(diags, :)
+
+o2n = n
+co2n = n
+
+for i in 1:w
+    global o2gen, co2scrub, o2n, co2n
+    is_one_at_i(s) = s[i] == '1' ? true : false
+    is_zero_at_i(s) = s[i] == '0' ? true : false
+    o2idx_ones = findall(is_one_at_i, o2gen)
+    co2idx_ones = findall(is_one_at_i, co2scrub)
+
+    if length(o2gen) > 1
+        if length(o2idx_ones) >= o2n/2
+            o2gen = o2gen[o2idx_ones]
+        else
+            o2gen = o2gen[findall(is_zero_at_i, o2gen)]
+        end
+        o2n = length(o2gen)
+    end
+
+    if length(co2scrub) > 1
+        if length(co2idx_ones) < co2n/2
+            co2scrub = co2scrub[co2idx_ones]
+        else
+            co2scrub = co2scrub[findall(is_zero_at_i, co2scrub)]
+        end
+        co2n = length(co2scrub)
+    end
+end
+
+o2gen_v = parse(Int, o2gen[1], base=2)
+co2scrub_v = parse(Int, co2scrub[1], base=2)
+println("o2gen ", o2gen, " ", o2gen_v)
+println("co2scrub ", co2scrub, " ", co2scrub_v)
+println("prod ", o2gen_v * co2scrub_v)

day3test.txt

@@ -0,0 +1,12 @@
+00100
+11110
+10110
+10111
+10101
+01111
+00111
+11100
+10000
+11001
+00010
+01010