# LeetCode - 0560. Subarray Sum Equals K
### 題目網址：https://leetcode.com/problems/subarray-sum-equals-k/
###### tags: `LeetCode` `Medium`

/*
    -LeetCode format-
    Problem: 560. Subarray Sum Equals K
    Difficulty: Medium
    
    by Inversionpeter
*/



class Solution {
public:
    int subarraySum(vector<int>& nums, int k) {
        unordered_map <int, int> prefixs;
        int sums = 0, counts = 0;
        prefixs[0] = 1;
        for (int &i : nums) {
            sums += i;
            if (prefixs.count(sums - k))
                counts += prefixs[sums - k];
            ++prefixs[sums];
        }
        return counts;
    }
};