added: longest repeating character replacement

Author: mihirs16

14. Questions/leetcode 424 - longest repeating character replacement.py

@@ -0,0 +1,23 @@
+# longest repeating character replacement | leetcode 424 | https://leetcode.com/problems/longest-repeating-character-replacement/
+# keep track of max freq in sliding window and check if size of window - max freq > k
+
+class Solution:
+    def characterReplacement(self, s: str, k: int) -> int:
+        ptrL = 0
+        ptrR = 0
+        longest = 0
+        freq = dict()
+        max_freq = 0
+        w_size = 0
+
+        for ptrR in range(len(s)):
+            freq[s[ptrR]] = 1 + freq.get(s[ptrR], 0)
+            max_freq = max(max_freq, freq[s[ptrR]])
+
+            if (ptrR - ptrL + 1) - max_freq > k:
+                freq[s[ptrL]] -= 1
+                ptrL += 1
+
+            longest = max(longest, (ptrR - ptrL + 1))
+
+        return longest