From cbbee06a642be48e34ea589f6c050f8a6865c5f7 Mon Sep 17 00:00:00 2001
From: Dominic <git@msrd0.de>
Date: Wed, 13 Dec 2023 18:35:38 +0100
Subject: [PATCH] day 13 part 2

---
 src/bin/day13.rs | 76 +++++++++++++++++++++++++-----------------------
 1 file changed, 40 insertions(+), 36 deletions(-)

diff --git a/src/bin/day13.rs b/src/bin/day13.rs
index 6f2a434..66b8d78 100644
--- a/src/bin/day13.rs
+++ b/src/bin/day13.rs
@@ -1,4 +1,3 @@
-// #![allow(clippy::never_loop)]
 #![forbid(elided_lifetimes_in_paths, unsafe_code)]
 
 use aoc23::read;
@@ -43,51 +42,56 @@ fn parser() -> impl Parser<char, Vec<Pattern>, Error = Simple<char>> {
 		.then_ignore(end())
 }
 
-fn main() -> anyhow::Result<()> {
-	let patterns = read("inputs/day13.txt", parser())?;
-
+fn find_mirrors_in_patters(patterns: &[Pattern], diff: u32) -> usize {
 	let mut rows = Vec::new();
 	let mut cols = Vec::new();
-	for (pidx, Pattern { grid }) in patterns.iter().enumerate() {
-		eprintln!("Pattern {pidx}");
-		'i: for i in 1 .. grid.len() {
-			for j in 0 .. i.min(grid.len() - i) {
-				if grid[i - j - 1] != grid[i + j] {
-					// eprintln!("discarding cut {i} due to rows {}/{}", i - j - 1, i + j);
-					continue 'i;
-				}
-			}
-			println!("mirroring at row {i}");
-			rows.push(i);
-		}
-		// println!("rows: {rows:?}");
 
-		'i: for i in 1 .. grid[0].len() {
-			for j in 0 .. i.min(grid[0].len() - i) {
-				for row in grid {
-					if row[i - j - 1] != row[i + j] {
-						// eprintln!(
-						// 	"discarding cut {i} due to cols {}/{}",
-						// 	i - j - 1,
-						// 	i + j
-						// );
-						continue 'i;
+	for Pattern { grid } in patterns {
+		'i: for i in 1 .. grid.len() {
+			let mut d = 0;
+			for j in 0 .. i.min(grid.len() - i) {
+				assert_eq!(grid[0].len(), grid[i - j - 1].len());
+				assert_eq!(grid[0].len(), grid[i + j].len());
+				for k in 0 .. grid[0].len() {
+					if grid[i - j - 1][k] != grid[i + j][k] {
+						d += 1;
+						if d > diff {
+							continue 'i;
+						}
 					}
 				}
 			}
-			println!("mirroring at col {i}");
-			cols.push(i);
+			if d == diff {
+				rows.push(i);
+			}
 		}
-		// println!("cols: {cols:?}");
 
-		// break;
+		'i: for i in 1 .. grid[0].len() {
+			let mut d = 0;
+			for j in 0 .. i.min(grid[0].len() - i) {
+				for row in grid {
+					if row[i - j - 1] != row[i + j] {
+						d += 1;
+						if d > diff {
+							continue 'i;
+						}
+					}
+				}
+			}
+			if d == diff {
+				cols.push(i);
+			}
+		}
 	}
 
-	// 20464 is too low
-	println!(
-		"{}",
-		rows.iter().sum::<usize>() * 100 + cols.iter().sum::<usize>()
-	);
+	rows.iter().sum::<usize>() * 100 + cols.iter().sum::<usize>()
+}
+
+fn main() -> anyhow::Result<()> {
+	let patterns = read("inputs/day13.txt", parser())?;
+
+	println!("{}", find_mirrors_in_patters(&patterns, 0));
+	println!("{}", find_mirrors_in_patters(&patterns, 1));
 
 	Ok(())
 }