performans 🤓 (absolutely crazy)

2024/04/p1/main.rs

@@ -4,29 +4,23 @@ fn main() -> std::io::Result<()> {
     let args: Vec<_> = std::env::args().collect();
     let filename = &args[1];
 
-    let mut contents = String::new();
+    let mut contents = vec![];
     let mut file = File::open(filename)?;
-    file.read_to_string(&mut contents)?;
+    file.read_to_end(&mut contents)?;
 
     let a = Instant::now();
 
-    let lines: Vec<_> = contents.lines().collect();
+    let lines: Vec<_> = contents.split(|&b| b == b'\n').collect();
     let mut t = 0;
     for (i, ln) in lines.iter().enumerate() {
-        for (j, ch) in ln.chars().enumerate() {
-            if ch == 'X' {
+        for (j, &ch) in ln.iter().enumerate() {
+            if ch == b'X' {
                 let map = [-1, 0, 1].map(|i| [-1, 0, 1].map(|j| (i, j)));
                 for dir in map.as_flattened() {
-                    if dir.0 == 0 && dir.1 == 0 { continue; }
-                    let r = eq_in_dir(
-                        &lines
-                            .iter()
-                            .map(|ln| ln.chars().collect::<Vec<_>>())
-                            .collect::<Vec<_>>(),
-                        (j, i),
-                        *dir,
-                        "MAS".chars(),
-                    );
+                    if dir.0 == 0 && dir.1 == 0 {
+                        continue;
+                    }
+                    let r = eq_in_dir(&lines, (j, i), *dir, "MAS".bytes());
                     if r {
                         t += 1;
                     }
@@ -42,19 +36,19 @@ fn main() -> std::io::Result<()> {
 }
 
 fn eq_in_dir(
-    buf: &[Vec<char>],
+    buf: &[&[u8]],
     pos: (usize, usize),
     dir: (isize, isize),
-    matches: impl Iterator<Item = char>,
+    matches: impl Iterator<Item = u8>,
 ) -> bool {
     opt_eq_in_dir(buf, pos, dir, matches).is_some()
 }
 
 fn opt_eq_in_dir(
-    buf: &[Vec<char>],
+    buf: &[&[u8]],
     pos: (usize, usize),
     dir: (isize, isize),
-    mut matches: impl Iterator<Item = char>,
+    mut matches: impl Iterator<Item = u8>,
 ) -> Option<()> {
     let Some(must_match) = matches.next() else {
         return Some(());