day 3

src/day_3.jl

@@ -0,0 +1,48 @@
+include(joinpath(readchomp(`git rev-parse --show-toplevel`), "aoc.jl"))
+import .Aoc: @aoc
+
+
+function p1(input::Vector{String})
+  o = [[],[],[],[],[],[],[],[],[],[],[],[]]
+  for l in input
+    c = match(r"(\d)(\d)(\d)(\d)(\d)(\d)(\d)(\d)(\d)(\d)(\d)(\d)", l).captures
+    for i in 1:12
+      push!(o[i], c[i])
+    end
+  end
+  γ = ""
+  ϵ = ""
+  for n in o
+    γ *= count(==("1"), n) > count(==("0"), n) ? "1" : "0"
+    ϵ *= count(==("1"), n) > count(==("0"), n) ? "0" : "1"
+  end
+  parse(Int, γ; base=2) * parse(Int, ϵ; base=2)
+end
+
+
+function p2(input::Vector{String})
+  i1 = deepcopy(input)
+  i2 = deepcopy(input)
+  ox = ""
+  co = ""
+  for i in 1:length(input[1])
+    oxbits = map(x -> x[i], i1)
+    oxmc = count(==('1'), oxbits) >= count(==('0'), oxbits) ? '1' : '0'
+    filter!(x -> x[i] == oxmc, i1)
+
+    cobits = map(x -> x[i], i2)
+    comc = count(==('1'), cobits) >= count(==('0'), cobits) ? '0' : '1'
+    filter!(x -> x[i] == comc, i2)
+
+    if length(i1) == 1 && ox == ""
+      ox = i1[begin]
+    end
+
+    if length(i2) == 1 && co == ""
+      co = i2[begin]
+    end
+  end
+  parse(Int, ox; base=2) * parse(Int, co; base=2)
+end
+
+@aoc(2021, 3)