From 443ff2cee67a187244e7eee1804e8b31e13da179 Mon Sep 17 00:00:00 2001
From: Bert Peters <bert@bertptrs.nl>
Date: Sun, 1 Dec 2024 18:04:13 +0100
Subject: [PATCH] Reduce part 2 to O(n)

---
 2024/bonus/day01/main.tf | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/2024/bonus/day01/main.tf b/2024/bonus/day01/main.tf
index 41fd6b1..9eebb15 100644
--- a/2024/bonus/day01/main.tf
+++ b/2024/bonus/day01/main.tf
@@ -14,7 +14,9 @@ locals {
 
   diffs = [for i in range(length(local.left_sorted)): abs(local.left_sorted[i] - local.right_sorted[i])]
 
-  matching = [for left in local.left: sum([for right in local.right: left == right ? left : 0])]
+  counts = {for num in local.right: num => num...}
+
+  matching = [for left in local.left: left * length(lookup(local.counts, left, []))]
 }
 
 output "part1" {