Example 1:
Input: nums = [1,1,1], k = 2
Output: 2
Explanation:
Example 2:
Input: nums = [1,2,3], k = 3
Output: 2
Explanation:
Example 3:
Input: nums = [1,-1,0], k = 0
Output: 3
Explanation:
Given an integer array nums and an integer k, return the total number of contiguous subarrays whose sum equals k.
A subarray is a contiguous non-empty sequence of elements within the array. The array may contain negative numbers and zeros.
The subarrays [1,1] at indices 0..1 and 1..2 both sum to 2.
[1,2] sums to 3 and [3] sums to 3.
[1,-1], [1,-1,0], and [0] all sum to 0.
1 <= nums.length <= 2 * 10^4-1000 <= nums[i] <= 1000-10^7 <= k <= 10^7