560\. Subarray Sum Equals K

Medium

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:**

*   <code>1 <= nums.length <= 2 * 10<sup>4</sup></code>
*   `-1000 <= nums[i] <= 1000`
*   <code>-10<sup>7</sup> <= k <= 10<sup>7</sup></code>