Subarray Sum Equals K

Given an integer array nums and an integer k, return the total number of subarrays whose sum equals k.

A subarray is a contiguous non-empty sequence of elements within an array.

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Example 1

Input: nums = [1, 1, 1], k = 2
Output: 2
Explanation: The subarrays [1, 1] (indices 0-1) and [1, 1] (indices 1-2) each sum to 2.

Example 2

Input: nums = [1, 2, 3], k = 3
Output: 2
Explanation: The subarrays [3] (index 2) and [1, 2] (indices 0-1) each sum to 3.

Example 3

Input: nums = [1], k = 1
Output: 1
Explanation: The only subarray [1] sums to 1.

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Constraints

• 1 <= nums.length <= 2 * 10^4
• -1000 <= nums[i] <= 1000
• -10^7 <= k <= 10^7