题目
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, 10^8]

答案

class Solution {
    private void s_swap(StringBuilder sb, int i, int j) {
        char t = sb.charAt(i);
        sb.setCharAt(i, sb.charAt(j));
        sb.setCharAt(j, t);
    }
    public int maximumSwap(int num) {
        StringBuilder sb = new StringBuilder(Integer.toString(num));
        String max = sb.toString();
        for(int i = 0; i < sb.length(); i++) {
            for(int j = 0; j < sb.length(); j++) {
                if(i == j) continue;
                s_swap(sb, i, j);
                String t = sb.toString();
                if(t.compareTo(max) > 0) {
                    max = t;
                }
                s_swap(sb, i, j);
            }
        }
        return Integer.parseInt(max);
    }
}