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# Subarray Sum

LintCode 138

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

Prefix sum 首题。这题用 prefix sum 和 hash map 解。

```python
    def subarraySum(self, nums):
        prefix = 0
        hashmap = {0:0}
        for i in range(len(nums)):
            prefix += nums[i]
            if prefix in hashmap:
                return [hashmap[prefix], i]
            hashmap[prefix] = i + 1

        return [-1, -1]
```