1323. Maximum 69 Number

QUESTION:

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.

EXPLANATION:

emmmm,因为今天的题目是之前已经做过的了，所以就做了一道easy的题目，题意也比较简单，只能对数字进行至多一次的翻转，所以我们可以想到，从最高位开始，遇到6就进行一次翻转就可以。

SOLUTION:

class Solution {
    public int maximum69Number (int num) {
        char[] chars = String.valueOf(num).toCharArray();
        boolean find = false;

        for(int i = 0;i<chars.length;i++){
            if(!find && chars[i] == '6') {
                chars[i] = '9';
                find = true;
            }
        }
        return Integer.parseInt(String.valueOf(chars));
    }
}
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