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
Note:
- 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 n=nums.size(); if (n==0) return 0; vector<int> sum(n+1,0); for (int i=1; i<=n; i++) sum[i]=nums[i-1]+sum[i-1]; unordered_map<int,int> hash; hash[0]=1; int res=0; for (int i=1; i<=n; i++) { if (hash[sum[i]-k]) res+=hash[sum[i]-k]; hash[sum[i]]++; } return res; } };