# Subarray Sum

LintCode-138.Subarray Sum

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.

Notice: There is at least one subarray that it's sum equals to zero.

Have you met this question in a real interview? Yes
Example: Given [-3, 1, 2, -3, 4], return [0, 2] or [1, 3].

``````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) {
ArrayList<Integer> result = new ArrayList<>();

if (nums == null || nums.length == 0) {
return result;
}

int sum = 0;
HashMap<Integer, Integer> map = new HashMap<>();

for (int i = 0; i < nums.length; i++) {
sum += nums[i];

if (sum == 0) {
result.add(0);
result.add(i);
break;
}

if (map.containsKey(sum)) {
result.add(map.get(sum) + 1);
result.add(i);
break;
}

map.put(sum, i);
}

return result;
}
}
``````

Hope this helps,
Michael