Interleaving Positive and Negative Numbers

Given an array with positive and negative integers. Re-range it to interleaving with positive and negative integers.

Note: You are not necessary to keep the original order of positive integers or negative integers.

Example

Given [-1, -2, -3, 4, 5, 6], after re-range, it will be[-1, 5, -2, 4, -3, 6] or any other reasonable answer.

分析：

其实这题思路还是很简单的，先用partition方法把数组分成两队，左边的数是小于0的数，右边的数是大于0的数。

然后，我们需要把正数插入到负数里，但是之前我们要确认正数负数哪个更多。多的要放在第一个位置。

 class Solution {
     /**
      * @param A: An integer array.
      * @return: void
      * cnblogs.com/beiyeqingteng/
      */
     public void rerange(int[] A) {
         if (A == null || A.length <= ) return;
         int pp = partition(A);  //positive number starting posisition
         int np = ; // negatie number starting position
         if (A.length /  < pp) {
             np++;
         }
         // put positive numbers into negative numbers
         while (np <= A.length -  && pp <= A.length - ) {
             swap(A, np, pp);
             np = np + ;
             pp++;
         }
    }

    // move negative to left
    private int partition(int[] A) {
        int p = ;
        for (int i = ; i < A.length; i++) {
            if (A[i] < ) {
                swap(A, i, p);
                p++;
            }
        }
        return p;
    }

    private void swap(int[] A, int i, int j) {
        int temp = A[i];
        A[i] = A[j];
        A[j] = temp;
    }
 }

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