src/main/java/com/fishercoder/solutions/_1323.java

package com.fishercoder.solutions;

import java.util.stream.IntStream;

/**
 * 1323. Maximum 69 Number
 *
 * Given a positive integer num consisting only of digits 6 and 9.
 * Return the maximum number you can get by changing at most one digit (6 becomes 9, and 9 becomes 6).
 *
 * Example 1:
 * Input: num = 9669
 * Output: 9969
 * Explanation:
 * Changing the first digit results in 6669.
 * Changing the second digit results in 9969.
 * Changing the third digit results in 9699.
 * Changing the fourth digit results in 9666.
 * The maximum number is 9969.
 *
 * Example 2:
 * Input: num = 9996
 * Output: 9999
 * Explanation: Changing the last digit 6 to 9 results in the maximum number.
 *
 * Example 3:
 * Input: num = 9999
 * Output: 9999
 * Explanation: It is better not to apply any change.
 *
 * Constraints:
 * 1 <= num <= 10^4
 * num's digits are 6 or 9.
 * */
public class _1323 {
    public static class Solution1 {
        public int maximum69Number(int num) {
            char[] chars = Integer.toString(num).toCharArray();
            IntStream.range(0, chars.length).filter(i -> chars[i] == '6').findFirst().ifPresent(i -> chars[i] = '9');
            return Integer.parseInt(new String(chars));
        }
    }
}