670. Maximum Swap

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]

只交换一次整数中的两个数，获得最大的值

思路：从高位向低扫描，如果后面某位的数大于等于当前位的值，交换位置后即得到最大值。

 1     public int maximumSwap(int num) {
 2 //        从高位向低扫描，如果后面某位的数大于等于当前位的值，交换位置后即得到最大值
 3         char[] dig = String.valueOf(num).toCharArray();
 4         int maxIndex = 0;
 5         while (maxIndex < dig.length - 1) {
 6             int newMaxIndex = maxIndex;
 7             for (int i = maxIndex + 1; i < dig.length; i++) {
 8                 if (dig[newMaxIndex] <= dig[i])  newMaxIndex = i;
 9             }
10             if (newMaxIndex != maxIndex && dig[newMaxIndex] != dig[maxIndex]) {
11                 char temp = dig[newMaxIndex];
12                 dig[newMaxIndex] = dig[maxIndex];
13                 dig[maxIndex] = temp;
14                 return Integer.valueOf(new String(dig));
15             }else  maxIndex++;//当前maxIndex的后面没有大于等于它的数字了
16         }
17         return num;
18     }