Zero_Sum_Subarrays.cpp

/*
Problem Statement:
-----------------
You are given an array arr[] of size n. Find the total count of sub-arrays having their sum equal to 0.

Example 1:
---------
Input:
n = 6
arr[] = {0,0,5,5,0,0}
Output: 6
Explanation: The 6 subarrays are [0], [0], [0], [0], [0,0], and [0,0].

Example 2:
---------
Input:
n = 10
arr[] = {6,-1,-3,4,-2,2,4,6,-12,-7}
Output: 4
Explanation: The 4 subarrays are [-1 -3 4] [-2 2], [2 4 6 -12], and [-1 -3 4 -2 2]

Your Task:
You don't need to read input or print anything. Complete the function findSubarray() that takes the array arr and its size n as input parameters and 
returns the total number of sub-arrays with 0 sum. 
 
Expected Time Complexity: O(n*log(n))
Expected Auxilliary Space: O(n)
 
Constraints:    
1 <= n <= 10^6
-10^9 <= arr[ i ] <= 10^9
*/

// Link --> https://practice.geeksforgeeks.org/problems/zero-sum-subarrays1825/1

// Code:
class Solution{
public:
    //Function to count subarrays with sum equal to 0.
    long long int findSubarray(vector<long long int> &arr, int n ) {
        long long int counter=0,sum=0;
        unordered_map <long long int , long long int> mp;
        for(int i=0;i<n;i++){
            sum+=arr[i];    
            if(sum==0) 
		    counter++;
            if(mp.count(sum)!=0) 
		    counter+=mp[sum];
            mp[sum]++;
        }
        return counter;
    }
};