private int segregate(int arr[]){
        int low =0;
        int high = arr.length-1;
        while(low < high){
            if(arr[low] < 0){
                low++;
            }else if(arr[high] >= 0){
                high--;
            }else{
                swap(arr,low,high);
            }
        }
        return low;
    }
http://www.geeksforgeeks.org/rearrange-positive-and-negative-numbers-publish/
src/com/interview/array/PositiveAndNegativeNumberAlternatively.java