renames

2023/day01/src/zero_alloc.rs

@@ -0,0 +1,43 @@
+pub fn part2(input: &str) -> u64 {
+    let sum = input
+        .lines()
+        .map(|line| {
+            let bytes = line.as_bytes();
+
+            let mut i = 0;
+            let mut first = None;
+            let mut last = b'_';
+
+            let mut insert = |byte| {
+                if first.is_none() {
+                    first = Some(byte);
+                }
+                last = byte;
+            };
+
+            while i < bytes.len() {
+                match bytes[i] {
+                    b @ b'0'..=b'9' => insert(b),
+                    b'o' if bytes.get(i..(i + 3)) == Some(b"one") => insert(b'1'),
+                    b't' if bytes.get(i..(i + 3)) == Some(b"two") => insert(b'2'),
+                    b't' if bytes.get(i..(i + 5)) == Some(b"three") => insert(b'3'),
+                    b'f' if bytes.get(i..(i + 4)) == Some(b"four") => insert(b'4'),
+                    b'f' if bytes.get(i..(i + 4)) == Some(b"five") => insert(b'5'),
+                    b's' if bytes.get(i..(i + 3)) == Some(b"six") => insert(b'6'),
+                    b's' if bytes.get(i..(i + 5)) == Some(b"seven") => insert(b'7'),
+                    b'e' if bytes.get(i..(i + 5)) == Some(b"eight") => insert(b'8'),
+                    b'n' if bytes.get(i..(i + 4)) == Some(b"nine") => insert(b'9'),
+                    _ => {}
+                }
+                i += 1;
+            }
+
+            let first = (first.unwrap() - b'0') as u64;
+            let last = (last - b'0') as u64;
+
+            first * 10 + last
+        })
+        .sum::<u64>();
+
+        sum
+    }