Zero sum subarray - Leetcode Solution

Solution

We can solve this problem by taking constructing a cumulative sum array and by using a hash table. Let the main array be called arr and cumulative sum array be called cu . cu will store the cumulative sum of all elements starting from position 0 till n - 1
Therefore, we can write: cu[k] = arr[0] + arr[1] + arr[2] + .... arr[k]
If the sum of subarray from index i + 1 till index j is 0, it means that cu[j] = cu[i] Therefore, we can create a hashmap with key as the sum and value as the index till which the sum was calculated, and check for duplicates.
See the below code for implementation.