From 40682f6cb67eb3aa6f440b2c2fdcfd868b17be2e Mon Sep 17 00:00:00 2001
From: Patrick Michl <patrick.michl@hetzner.com>
Date: Fri, 3 Dec 2021 09:26:46 +0100
Subject: [PATCH] optimize day 3

---
 src/day_3.jl | 40 ++++++++++++++++------------------------
 1 file changed, 16 insertions(+), 24 deletions(-)

diff --git a/src/day_3.jl b/src/day_3.jl
index 0d7456b..0e16021 100644
--- a/src/day_3.jl
+++ b/src/day_3.jl
@@ -3,44 +3,36 @@ 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"
+  for n in 1:length(input[1])
+    bits = map(x -> parse(Int, x[n]), input)
+    more_ones = sum(bits) > length(bits) / 2
+    γ *= more_ones ? "1" : "0"
+    ϵ *= more_ones ? "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)
+  i1 = copy(input)
+  i2 = copy(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)
+    oxbits = map(x -> parse(Int, x[i]), i1)
+    cobits = map(x -> parse(Int, x[i]), i2)
+    
+    oxmc = sum(oxbits) >= length(oxbits) / 2 ? '1' : '0'
+    comc = sum(cobits) >= length(cobits) / 2 ? '0' : '1'
 
-    cobits = map(x -> x[i], i2)
-    comc = count(==('1'), cobits) >= count(==('0'), cobits) ? '0' : '1'
+    filter!(x -> x[i] == oxmc, i1)
     filter!(x -> x[i] == comc, i2)
 
-    if length(i1) == 1 && ox == ""
-      ox = i1[begin]
-    end
-
-    if length(i2) == 1 && co == ""
-      co = i2[begin]
-    end
+    length(i1) == 1 && ox == "" ? (ox = i1[1]) : nothing
+    length(i2) == 1 && co == "" ? (co = i2[1]) : nothing
+    ox != "" && co != "" ? break : continue
   end
   parse(Int, ox; base=2) * parse(Int, co; base=2)
 end