longest-repeating-character-replacement

Author: DaleSeo

longest-repeating-character-replacement/DaleSeo.rs

@@ -0,0 +1,27 @@
+// TC: O(n), where n is s.len()
+// SC: O(1), fixed 26-slot frequency array
+impl Solution {
+    pub fn character_replacement(s: String, k: i32) -> i32 {
+        let bytes = s.as_bytes();
+        let mut counts = [0i32; 26];
+        let mut start = 0usize;
+        let mut max_freq = 0i32;
+        let mut result = 0i32;
+
+        for end in 0..bytes.len() {
+            let idx = (bytes[end] - b'A') as usize;
+            counts[idx] += 1;
+            max_freq = max_freq.max(counts[idx]);
+
+            while (end - start + 1) as i32 - max_freq > k {
+                let left_idx = (bytes[start] - b'A') as usize;
+                counts[left_idx] -= 1;
+                start += 1;
+            }
+
+            result = result.max((end - start + 1) as i32);
+        }
+
+        result
+    }
+}