Lintcode: 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 or 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 legal answer.

Challenge
Do it in-place and without extra memory.

这道题没有给出正数、负数谁多谁少，所以需要先统计数量，数量多的要包着数量少的，然后数组尾部全是数量多的数

class Solution {
    /**
     * @param A: An integer array.
     * @return an integer array
     */
    public int[] rerange(int[] A) {
        // write your code here
        int posNum = 0, negNum = 0;
        for (int elem : A) {
            if (elem < 0) {
                negNum++;
            }
            else {
                posNum++;
            }
        }
        int posInd = 1, negInd = 0;
        if (posNum > negNum) {
            negInd = 1;
            posInd = 0;
        }
        while (posInd<A.length && negInd<A.length) {
            while (posInd < A.length && A[posInd] > 0) {
                posInd += 2;
            }
            while (negInd < A.length && A[negInd] < 0) {
                negInd += 2;
            }
            if (posInd<A.length && negInd<A.length) {
                swap(A, posInd, negInd);

            }
        }
        return A;
   }
   
   public void swap(int[] A, int l, int r) {
       int temp = A[l];
       A[l] = A[r];
       A[r] = temp;
   }
}