Given an array of integers nums and an integer k, return the total number of continuous subarrays whose sum equals to k. Example 1: Input: nums = [1,1,1], k = 2 Output: 2 Example 2: Input: nums = [1,2,3], k = 3 Output: 2 Constraints: 1 <= nums.length <= 2 * 104 -1000 <= nums[i] <= 1000 -107 <= k <= 107