LintCode Subarray Sum 子数组之和

给定一个整数数组，找到和为零的子数组。你的代码应该返回满足要求的子数组的起始位置和结束位置。

样例
给出[-3, 1, 2, -3, 4]，返回[0, 2] 或者 [1, 3].

Given an integer array, find a subarray where the sum of numbers is zero. Your code should return the index of the first number and the index of the last number.

Example
Given [-3, 1, 2, -3, 4], return [0, 2] or [1, 3].

Note
There is at least one subarray that it’s sum equals to zero.

public class Solution {
    /**
     * @param nums: A list of integers
     * @return: A list of integers includes the index of the first number 
     *          and the index of the last number
     */
    public ArrayList<Integer> subarraySum(int[] nums) {
        if(null == nums) return null;
        for(int i = 0; i < nums.length; i++) {
            ArrayList<Integer> list = new ArrayList<Integer>();
            list.add(i);
            int sum = nums[i];
            if(sum == 0) {
                list.add(i);
                return list;
            }
            for(int j = i + 1; j < nums.length; j++) {
                sum += nums[j];
                if(sum == 0) {
                    list.add(j);
                    return list;
                }
            }
        }
        return null;
    }
}