Create 1323-maximum-69-number.java

Author: sanajitjana

Easy/1323-maximum-69-number.java

@@ -0,0 +1,29 @@
+/**
+ * 1323. Maximum 69 Number
+ * Difficulty: Easy
+ * URL: https://leetcode.com/problems/maximum-69-number/description/
+ *
+ * ---------------------
+ * Approach: Greedy (First '6' to '9')
+ * ---------------------
+ * - Convert the number to a character array.
+ * - Traverse from left to right and change the **first '6'** to '9'.
+ * - Break immediately since changing the leftmost '6' maximizes the number.
+ * - Convert the updated character array back to an integer and return it.
+ *
+ * Time Complexity:  O(n)   // where n = number of digits
+ * Space Complexity: O(n)   // for storing char array (can be seen as O(1) since digits ≤ 4)
+ */
+
+class Solution {
+    public int maximum69Number(int num) {
+        char[] digits = String.valueOf(num).toCharArray();
+        for (int i = 0; i < digits.length; i++) {
+            if (digits[i] == '6') {
+                digits[i] = '9';
+                break;
+            }
+        }
+        return Integer.parseInt(String.valueOf(digits));
+    }
+}