144. Interleaving Positive and Negative Numbers
     Given an array with positive and negative integers. Re-range it to interleaving with positive and 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.

Challenge
Do it in-place and without extra memory.

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

public void rerange(int[] A) {
        // write your code here
        int l = 0, r = A.length - 1;
        while(l < r){
            while(l < r && A[l] < 0){
                l++;
            }
            while(l < r && A[r] > 0){
                r--;
            }
            if(l < r){
                int temp = A[l];
                A[l] = A[r];
                A[r] = temp;
                l++;
                r--;
            }
        }
        if(l > A.length - l){          //根據正負數多少來交叉，能交叉，則正負數個數最多相差1
            interleave(A,1,A.length - 1);
        }else if(l < A.length - l){
            interleave(A,0,A.length - 2);
        }
        else{
            interleave(A,0,A.length - 1);
        }
    }
    public void interleave(int[] A, int start, int end){   
        while(start <= end){
            int temp = A[start];
            A[start] = A[end];
            A[end] = temp;
            start += 2;
            end -= 2;
        }
    }