From 744aa2fc729116aa476750b77cddc8ffe8060d01 Mon Sep 17 00:00:00 2001
From: kageru <kageru@encode.moe>
Date: Tue, 7 Dec 2021 14:06:09 +0100
Subject: [PATCH] Simplify day 7

---
 2021/src/bin/day07.rs | 28 ++++++----------------------
 1 file changed, 6 insertions(+), 22 deletions(-)

diff --git a/2021/src/bin/day07.rs b/2021/src/bin/day07.rs
index 8040d71..12d1a54 100644
--- a/2021/src/bin/day07.rs
+++ b/2021/src/bin/day07.rs
@@ -2,7 +2,6 @@
 #![feature(test)]
 extern crate test;
 use aoc2021::common::*;
-use itertools::{Itertools, MinMaxResult};
 
 const DAY: usize = 7;
 type Parsed = Vec<usize>;
@@ -11,25 +10,16 @@ fn parse_input(raw: &str) -> Parsed {
     parse_nums_comma(raw)
 }
 
-fn min_max(parsed: &Vec<usize>) -> (usize, usize) {
-    match parsed.iter().minmax() {
-        MinMaxResult::MinMax(&min, &max) => (min, max),
-        _ => unreachable!("List not long enough"),
-    }
-}
-
 fn part1(parsed: &Parsed) -> usize {
-    let (min, max) = min_max(parsed);
-    (min..=max).map(|x| parsed.iter().map(|p| p.abs_diff(x)).sum()).min().unwrap()
-}
-
-fn sum_to(n: usize) -> usize {
-    (1..=n).sum()
+    let mut nums = parsed.to_owned();
+    nums.sort();
+    let median = nums[nums.len() / 2];
+    parsed.iter().map(|p| p.abs_diff(median)).sum()
 }
 
 fn part2(parsed: &Parsed) -> usize {
-    let (min, max) = min_max(parsed);
-    (min..=max).map(|x| parsed.iter().map(|p| p.abs_diff(x)).map(sum_to).sum()).min().unwrap()
+    let avg = parsed.iter().sum::<usize>() / parsed.len();
+    parsed.iter().map(|p| p.abs_diff(avg)).map(|n| (0..=n).sum::<usize>()).sum()
 }
 
 fn main() {
@@ -46,13 +36,7 @@ mod tests {
     const TEST_INPUT: &str = "16,1,2,0,4,2,7,1,2,14";
 
     test!(part1() == 37);
-    test!(part2() == 168);
     bench!(part1() == 328318);
     bench!(part2() == 89791146);
     bench_input!(Vec::len => 1000);
-
-    #[bench]
-    fn bench_sum_to(b: &mut test::Bencher) {
-        b.iter(|| assert_eq!(sum_to(test::black_box(1000000)), 500000500000))
-    }
 }