# HG changeset patch
# User Jordi Gutiérrez Hermoso <jordigh@octave.org>
# Date 1513265798 18000
# Node ID 817954f71d53b8d63c19052bc297e565725df18c
# Parent  56b75b62d5913a834473ab3518a87631b85ef363
day 13: cache a calculation for speed

diff --git a/2017/day13.d b/2017/day13.d
--- a/2017/day13.d
+++ b/2017/day13.d
@@ -5,7 +5,7 @@
 import std.array: array;
 
 auto getHits(T)(T firewall, int init = 0) {
-  return firewall.filter!(xy => (init + xy[0]) % (2*(xy[1]-1)) == 0);
+  return firewall.filter!(xy => (init + xy[0]) % xy[2] == 0);
 }
 
 auto computeSeverity(T)(T firewall) {
@@ -22,7 +22,10 @@
 
 void main(string[] args) {
   auto firewall = File(args[1]).byLineCopy.map!(
-    x => x.split(": ").map!(to!int)
+    function(string x){
+      auto v = x.split(": ").map!(to!int);
+      return v.array ~ (2*v[1] - 2);
+    }
   ).array;
   writeln(firewall.computeSeverity);
   writeln(firewall.findPassing);