17. Subarray Sum Equals K

Medium · Array

Given an array of integers and a target sum k, count how many contiguous subarrays have a sum equal to k. A subarray must contain at least one element and consist of consecutive elements from the original array. For example, in [1,1,1] with k=2, the subarrays [1,1] at indices 0–1 and [1,1] at indices 1–2 both sum to 2, giving a count of 2.

Input: an array [nums, k] where nums is a list of integers and k is the target sum.

Return: the total count of contiguous subarrays whose sum equals k.

Examples

Example 1
Input: [[1,1,1], 2]
Output: 2
Explanation: Two subarrays of length 2 sum to 2

Example 2
Input: [[1,2,3], 3]
Output: 2
Explanation: [1,2] and [3]

Constraints

• Standard input/output constraints apply