From 00b5e44302eb0e846a0afe40cc25d2f1152214f3 Mon Sep 17 00:00:00 2001
From: Deepak ojha <59064357+Deepak3493@users.noreply.github.com>
Date: Tue, 23 Jun 2026 02:48:42 +0530
Subject: [PATCH] Implement characterReplacement method in Java

Added Java implementation for character replacement problem.
---
 ...03.LongestRepeatingCharacterReplacement.md | 24 +++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/03. Sliding Window/03.LongestRepeatingCharacterReplacement.md b/03. Sliding Window/03.LongestRepeatingCharacterReplacement.md
index 9949820..8cb4c48 100644
--- a/03. Sliding Window/03.LongestRepeatingCharacterReplacement.md	
+++ b/03. Sliding Window/03.LongestRepeatingCharacterReplacement.md	
@@ -63,3 +63,27 @@ class Solution {
     }
 }
 ```
+
+```java
+class Solution {
+    public int characterReplacement(String s, int k) {
+        int[] freqArray=new int[26]; // Storing Frequency of characters A-Z
+        int left=0, maxFreq=0,longestSubstring=0;
+        for(int right=0;right<s.length();right++){ //expanding right 
+            char ch=s.charAt(right);//take curr char
+            freqArray[ch-'A']++;//inc the freq of char in array
+            maxFreq=Math.max(maxFreq,freqArray[ch-'A']);//cal max freq acc to curr char 
+             // Characters needed to replace = windowSize - maxFreq
+             //and if replace >k then we shrink win until it becomes valid agn 
+            while((right-left+1)-maxFreq>k){
+                freqArray[s.charAt(left)-'A']--;// Remove left character from window
+                left++;
+            } 
+            //cal longest substing length
+            longestSubstring=Math.max(right-left+1,longestSubstring);
+        }
+        return longestSubstring;
+
+    }
+}
+```