1095. Maximum Swap —— Weekly Challenge

 1 public class Solution {
 2     /**
 3      * @param num: a non-negative intege
 4      * @return: the maximum valued number
 5      */
 6     public int maximumSwap(int num) {
 7         // Write your code here
 8         char[] numArrays = String.valueOf(num).toCharArray();
 9         if (numArrays.length < 2) {
10             return num;
11         }
12 
13         //第一个递增点:
14         int firstHeigerPoint = 0;
15         for (int i = 0; i < numArrays.length - 1; i++) {
16             if (numArrays[i] < numArrays[i + 1]) {
17                 firstHeigerPoint = i + 1;
18                 break;
19             }
20         }
21 
22         if (firstHeigerPoint == 0) {
23             return num;
24         }
25 
26         //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)
27         int max = numArrays[firstHeigerPoint];
28         int maxPoint = firstHeigerPoint;
29         for (int j = firstHeigerPoint; j < numArrays.length; j++) {
30             if (numArrays[j] >= max) {
31                 max = numArrays[j];
32                 maxPoint = j;
33             }
34         }
35 
36         //找到第一个更小的高位
37         int toSwapIndex = firstHeigerPoint-1;
38         for (int i = 0; i <= firstHeigerPoint - 1; i++) {
39             if (numArrays[i] < max) {
40                 toSwapIndex = i;
41                 break;
42             }
43         }
44         
45         
46 
47         char temp = numArrays[toSwapIndex];
48         numArrays[toSwapIndex] = numArrays[maxPoint];
49         numArrays[maxPoint] = temp;
50 
51         return Integer.parseInt(new String(numArrays));
52     }
53 }