Add longest repeating char replacement solution

Author: sudheerj

src/java1/algorithms/strings/longestRepeatingCharReplacement.java

@@ -0,0 +1,26 @@
+//Sliding window: TC:O(n) SC: O(1)
+package java1.algorithms.strings;
+
+public class longestRepeatingCharReplacement {
+    private static int longestCharReplacement(String str, int target) {
+        int[] charCount = new int[26];
+        int maxLength = 0;
+        int maxCharFrequency = 0;
+        int left =0;
+
+        for(int right = 0; right < str.length(); right++) {
+            maxCharFrequency = Math.max(maxCharFrequency, ++charCount[str.charAt(right) - 'A']);
+            while((right - left + 1 - maxCharFrequency) > target) {
+                charCount[str.charAt(left) - 'A']--;
+                left++;
+            }
+            maxLength = Math.max(maxLength, right-left+1);
+        }
+        return maxLength;
+    }
+
+    public static void main(String[] args) {
+        String str = "AAABABBAA";
+        System.out.println(longestCharReplacement(str, 2));
+    }
+}

src/javascript/algorithms/strings/longestRepeatingCharReplacement.js

@@ -0,0 +1,21 @@
+//Sliding window: TC:O(n) SC: O(1)
+function longestCharReplacement(str, target) {
+    let charFrequency = new Array(26).fill(0);;
+    let maxLength = 0, maxFrequency = 0;
+    let left = 0;
+
+    for(let right = 0; right < str.length; right++) {
+        maxFrequency = Math.max(maxFrequency, ++charFrequency[str.charCodeAt(right) - "A".charCodeAt(0)]);
+        while((right-left+1-maxFrequency) > target) {
+            charFrequency[str.charCodeAt(left) - "A".charCodeAt(0)]--;
+            left++;
+        }
+        maxLength = Math.max(maxLength, right-left+1);
+    }
+    return maxLength;
+}
+
+let str1 = "AAABABBAA";
+console.log(longestCharReplacement(str1, 2));
+let str2 = "BBBB";
+console.log(longestCharReplacement(str2, 2));