Added longest repeating character solution

Author: nhistory

longest-repeating-character-replacement/nhistory.js

@@ -0,0 +1,27 @@
+var characterReplacement = function (s, k) {
+  // Create two pointer to check repeating chracter (left, right)
+  let left = 0,
+    right = 0,
+    maxCount = 0,
+    map = new Map();
+
+  while (right < s.length) {
+    // Save each character into map and check how many time they have
+    map.set(s[right], map.get(s[right]) ? map.get(s[right]) + 1 : 1);
+    maxCount = Math.max(maxCount, map.get(s[right]));
+
+    // Count (right-left+1-k) and compare maximum value
+    if (right - left + 1 - k > maxCount) {
+      // Decrement value of map[s[left]] and move left pointer
+      map.set(s[left], map.get(s[left]) - 1);
+      left++;
+    }
+
+    right++;
+  }
+
+  return right - left;
+};
+
+// TC: O(n)
+// SC: O(1)