1 class Solution {
 2    /**
 3      * @param A: An integer array.
 4      * @return an integer array
 5      */
 6     // SOLUTION 2: 判断正数多还是负数多。 
 7     public static int[] rerange(int[] A) {
 8         // write your code here
 9         
10         // Check the input parameter.
11         if (A == null || A.length == 0) {
12             return A;
13         }
14         
15         int len = A.length;
16         
17         int left = -1;
18         int right = A.length;
19         
20         // divide the negative and positive integers.
21         while (true) {
22             while (left < A.length - 1 && A[++left] < 0);
23             
24             while (left < right && A[--right] > 0);
25             
26             if (left >= right) {
27                 break;
28             }
29             
30             swap(A, left, right);
31         }
32         
33         // LEFT: point to the first positive number.
34         int negNum = left;
35         int posNum = len - left;
36         
37         int les = Math.min(negNum, posNum);
38         int dif = Math.abs(negNum - posNum);
39         
40         // 如果负数比较多，把多的负数扔到后面去
41         if (negNum > posNum) {
42             int cnt = dif;
43             int l = les;
44             int r = len - 1;
45             while (cnt > 0) {
46                 swap(A, l, r);
47                 l++;
48                 r--;
49                 cnt--;
50             }
51             
52             // 负数多的时候，负数在前，反之，正数在前
53             left = -1;
54             // 跳过右边不需要交换的值
55             right = A.length - dif;
56         } else {
57             // 正数在前
58             left = -2;
59             // 跳过右边不需要交换的值
60             right = A.length - dif + 1;
61         }
62         
63         /*
64           -1 -2 -5 -6  3  4  les = 2;
65           4  -2 -5 -6  3 -1
66         */
67         // swap the negative and the positive
68         while (true) {
69             left += 2;
70             right -= 2;
71             
72             if (left >= les) {
73                 break;
74             }
75             swap(A, left, right);
76         }
77 
78         return A;
79    }
80    
81    public static void swap(int[] A, int n1, int n2) {
82        int tmp = A[n1];
83        A[n1] = A[n2];
84        A[n2] = tmp;
85    }
86 }