public class Solution {

     /**

      * @param num: a non-negative intege

      * @return: the maximum valued number

      */

     public int maximumSwap(int num) {

         // Write your code here

         char[] numArrays = String.valueOf(num).toCharArray();

         if (numArrays.length < 2) {

             return num;

         }

         //第一个递增点:

         int firstHeigerPoint = 0;

         for (int i = 0; i < numArrays.length - 1; i++) {

             if (numArrays[i] < numArrays[i + 1]) {

                 firstHeigerPoint = i + 1;

                 break;

             }

         }

         if (firstHeigerPoint == 0) {

             return num;

         }

         //找到递增点后的最大值(如有相等情况取低位，因而更新条件是numArrays[j] >= max)

         int max = numArrays[firstHeigerPoint];

         int maxPoint = firstHeigerPoint;

         for (int j = firstHeigerPoint; j < numArrays.length; j++) {

             if (numArrays[j] >= max) {

                 max = numArrays[j];

                 maxPoint = j;

             }

         }

         //找到第一个更小的高位

         int toSwapIndex = firstHeigerPoint-1;

         for (int i = 0; i <= firstHeigerPoint - 1; i++) {

             if (numArrays[i] < max) {

                 toSwapIndex = i;

                 break;

             }

         }

         char temp = numArrays[toSwapIndex];

         numArrays[toSwapIndex] = numArrays[maxPoint];

         numArrays[maxPoint] = temp;

         return Integer.parseInt(new String(numArrays));

     }

 }