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.

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) {
        // write your code here
        ArrayList<Integer> result = new ArrayList<Integer>();
        if (nums == null || nums.length == 0) return result;

        HashMap<Integer, Integer> map = new HashMap<Integer, Integer>();
        map.put(0, -1);//must consider the possibility that sum is zero already
        int sum = 0;
        for (int i = 0; i < nums.length; i++) {
            sum += nums[i];
            if (map.containsKey(sum)) {
                result.add(map.get(sum) + 1);
                result.add(i);
                return result;
            } else {
                map.put(sum, i);
            }
        }
        return result;
    }
}

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
    """
    def subarraySum(self, nums):
        # write your code here
        if not nums:
            return []

        sum_map = {0 : -1}
        #summation1 - summation2 = 0
        #summation1 and summation2 could both be zero
        summation = 0
        ret = []
        for i in xrange(len(nums)):
            summation += nums[i]
            if summation in sum_map:
                ret = [sum_map.get(summation) + 1, i]
                break
            else:
                sum_map[summation] = i
        return ret