560. Subarray Sum Equals K

class Solution {
public:
    int subarraySum(vector<int>& nums, int k) {
        unordered_map<int,int> m;
        int sum = 0;
        int count = 0;
        m[0] = 1;

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

            if(m.find(sum - k) != m.end()){
                count += m[sum - k];
            }

            m[sum]++;
        }

        return count;
    }
};