improve day04

1 files changed, 34 insertions, 81 deletions

diff --git a/2024/day04.rs b/2024/day04.rs
index f4dc88f..67f18b9 100644
--- a/2024/day04.rs
+++ b/2024/day04.rs
@@ -1,77 +1,23 @@
 #![allow(dead_code)]
 #![allow(unused_variables)]
 #![allow(unused_mut)]
+use itertools::Itertools;
+use std::cmp::max;
 use std::env;
 use std::fs::File;
 use std::io::Read;
 
-fn horizontal(lx: usize, ly: usize, m: &Vec<Vec<char>>) -> usize {
+fn xmas(s: &[char], xy: &[(usize, usize)], m: &Vec<Vec<char>>) -> usize {
     let mut count = 0;
-    for y in 0..ly {
-        for x in 0..lx - 3 {
-            if m[y][x] == 'X' && m[y][x + 1] == 'M' && m[y][x + 2] == 'A' && m[y][x + 3] == 'S' {
-                count += 1;
-            }
-            if m[y][x] == 'S' && m[y][x + 1] == 'A' && m[y][x + 2] == 'M' && m[y][x + 3] == 'X' {
-                count += 1;
-            }
-        }
-    }
-    count
-}
-
-fn vertical(lx: usize, ly: usize, m: &Vec<Vec<char>>) -> usize {
-    let mut count = 0;
-    for y in 0..ly - 3 {
-        for x in 0..lx {
-            if m[y][x] == 'X' && m[y + 1][x] == 'M' && m[y + 2][x] == 'A' && m[y + 3][x] == 'S' {
-                count += 1;
-            }
-            if m[y][x] == 'S' && m[y + 1][x] == 'A' && m[y + 2][x] == 'M' && m[y + 3][x] == 'X' {
-                count += 1;
-            }
-        }
-    }
-    count
-}
-
-fn diag1(lx: usize, ly: usize, m: &Vec<Vec<char>>) -> usize {
-    let mut count = 0;
-    for y in 0..ly - 3 {
-        for x in 0..lx - 3 {
-            if m[y][x] == 'X'
-                && m[y + 1][x + 1] == 'M'
-                && m[y + 2][x + 2] == 'A'
-                && m[y + 3][x + 3] == 'S'
-            {
-                count += 1;
-            }
-            if m[y][x] == 'S'
-                && m[y + 1][x + 1] == 'A'
-                && m[y + 2][x + 2] == 'M'
-                && m[y + 3][x + 3] == 'X'
-            {
-                count += 1;
-            }
-        }
-    }
-    count
-}
-fn diag2(lx: usize, ly: usize, m: &Vec<Vec<char>>) -> usize {
-    let mut count = 0;
-    for y in 0..ly - 3 {
-        for x in 0..lx - 3 {
-            if m[y][x + 3] == 'X'
-                && m[y + 1][x + 2] == 'M'
-                && m[y + 2][x + 1] == 'A'
-                && m[y + 3][x] == 'S'
-            {
-                count += 1;
-            }
-            if m[y][x + 3] == 'S'
-                && m[y + 1][x + 2] == 'A'
-                && m[y + 2][x + 1] == 'M'
-                && m[y + 3][x] == 'X'
+    let mx: usize = xy.iter().fold(0, |a, (x, y)| max(a, *x));
+    let my: usize = xy.iter().fold(0, |a, (x, y)| max(a, *y));
+    for r in 0..m.len() - my {
+        for c in 0..m[0].len() - mx {
+            if xy
+                .iter()
+                .enumerate()
+                .map(|(n, (x, y))| m[r + y][c + x] == s[n])
+                .all(|a| a)
             {
                 count += 1;
             }
@@ -80,10 +26,10 @@ fn diag2(lx: usize, ly: usize, m: &Vec<Vec<char>>) -> usize {
     count
 }
 
-fn mas(lx: usize, ly: usize, m: &Vec<Vec<char>>) -> usize {
+fn cross_mas(m: &Vec<Vec<char>>) -> usize {
     let mut count = 0;
-    for y in 1..ly - 1 {
-        for x in 1..lx - 1 {
+    for y in 1..m.len() - 1 {
+        for x in 1..m[0].len() - 1 {
             if m[y][x] != 'A' {
                 continue;
             }
@@ -93,12 +39,13 @@ fn mas(lx: usize, ly: usize, m: &Vec<Vec<char>>) -> usize {
                 m[y + 1][x + 1],
                 m[y + 1][x - 1],
             ];
-            if a == ['M', 'M', 'S', 'S']
-                || a == ['S', 'M', 'M', 'S']
-                || a == ['S', 'S', 'M', 'M']
-                || a == ['M', 'S', 'S', 'M']
-            {
-                count += 1;
+            let mut m = ['M', 'M', 'S', 'S'];
+            for r in 0..4 {
+                if a == m {
+                    count += 1;
+                    break;
+                }
+                m.rotate_right(1);
             }
         }
     }
@@ -130,13 +77,19 @@ fn main() {
     let ly = m.len();
     let lx = m[0].len();
 
-    let mut res1 = 0;
-    res1 += horizontal(lx, ly, &m);
-    res1 += vertical(lx, ly, &m);
-    res1 += diag1(lx, ly, &m);
-    res1 += diag2(lx, ly, &m);
+    let s: Vec<char> = "XMAS".chars().collect();
+    let sr: Vec<char> = s.clone().into_iter().rev().collect();
+    let horiz: [(usize, usize); 4] = [(0, 0), (1, 0), (2, 0), (3, 0)];
+    let vert: [(usize, usize); 4] = [(0, 0), (0, 1), (0, 2), (0, 3)];
+    let diag1: [(usize, usize); 4] = [(0, 0), (1, 1), (2, 2), (3, 3)];
+    let diag2: [(usize, usize); 4] = [(3, 0), (2, 1), (1, 2), (0, 3)];
+    let res1: usize = [s, sr]
+        .into_iter()
+        .cartesian_product([horiz, vert, diag1, diag2].into_iter())
+        .map(|(s, d)| xmas(&s, &d, &m))
+        .sum();
 
-    let res2 = mas(lx, ly, &m);
+    let res2 = cross_mas(&m);
 
     println!("res1: {}", res1);
     println!("res2: {}", res2);