Given a non-negative integer, you could swap two digits at most once to get the maximum valued number. Return the maximum valued number you could get. Example 1: Input: 2736 Output: 7236 Explanation: Swap the number 2 and the number 7. Example 2: Input: 9973 Output: 9973 Explanation: No swap. Note: The given number is in the range [0, 108]