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) { unordered_map<int,int> sumTracker; int ret =0; int sum =0; sumTracker[0] = 1; for(auto& num: nums) { sum += num; if(sumTracker[sum - k]) { ret += sumTracker[sum - k] ; } sumTracker[sum]++; } return ret; } };