solve

Author: sonjh1217

longest-repeating-character-replacement/sonjh1217.swift

@@ -0,0 +1,26 @@
+class Solution {
+    // O(n) time / O(n) space
+    func characterReplacement(_ s: String, _ k: Int) -> Int {
+        var windowStart = 0
+        var maxLength = 0
+        var maxCharacterRepeat = 0
+        var countByCharacter = [Character: Int]()
+        var characters = Array(s)
+        
+        for windowEnd in 0..<characters.count {
+            countByCharacter[characters[windowEnd], default: 0] += 1
+            maxCharacterRepeat = max(maxCharacterRepeat, countByCharacter[characters[windowEnd]]!)
+            
+            var length = windowEnd - windowStart + 1
+            if length - maxCharacterRepeat <= k {
+                maxLength = max(maxLength, length)
+            } else {
+                while (windowEnd - windowStart + 1) - maxCharacterRepeat > k {
+                    countByCharacter[characters[windowStart]]! -= 1
+                    windowStart += 1
+                }
+            }
+        }
+        return maxLength
+    }
+}