Maximum 69 Number

Problem Description

You are 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

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.

Constraints

• 1 <= num <= 104

Solution Approach

Intuition:

To efficiently determine the maximum number

Solution Implementation

Code (C++):

class Solution {
public:
    int maximum69Number (int num) {
        string str = to_string(num);
        for(int i = 0; i < str.size(); i++){
            if(str[i] == '6'){
                str[i] = '9';
                break;
            }
        }
        return stoi(str);
    }
};