Add longest-repeating-character-replacement solution

Author: Jeehay28

longest-repeating-character-replacement/Jeehay28.js

@@ -0,0 +1,32 @@
+/**
+ * @param {string} s
+ * @param {number} k
+ * @return {number}
+ */
+
+// sliding window technique
+// Time complexity: O(n), where n is the length of the string. Both the start and end pointers traverse the string at most once.
+// Space Complexity: O(1), as we only need a fixed amount of extra space for the character frequency map and some variables.
+var characterReplacement = function (s, k) {
+  let longest = 0;
+  let maxCount = 0;
+  const charCount = {};
+  let start = 0;
+
+  for (let end = 0; end < s.length; end++) {
+    const char = s[end];
+    charCount[char] = (charCount[char] || 0) + 1;
+    maxCount = Math.max(charCount[char], maxCount);
+
+    while (end - start + 1 - maxCount > k) {
+      const temp = s[start];
+      charCount[temp] -= 1;
+      start += 1;
+    }
+
+    longest = Math.max(longest, end - start + 1);
+  }
+
+  return longest;
+};
+