Subarray Sum Equals K

 

 

 Subarray Sum Equals K

Given an array of integers and an integer k, you need to find the total number of continuous subarrays whose sum equals to k.

Example 1:

Input:nums = [1,1,1], k = 2
Output: 2

 

Constraints:

• The length of the array is in range [1, 20,000].
• The range of numbers in the array is [-1000, 1000] and the range of the integer k is [-1e7, 1e7].

 

class Solution {
public:
    int subarraySum(vector<int>& nums, int k) {
        int l=0,curr=0;
        unordered_map<int,int> mp;
        
        for(int i=0;i<nums.size();++i)
        {
            curr+=nums[i];
            
            if(curr-k==0)
                  ++l;
            if(mp[curr-k])
                l+=mp[curr-k];
              mp[curr]++;
            
        }
        return l;
        
    }
};