Given an integer array nums and an integer k, return the maximum length of a subarray that sums to k. If there isn't one, return 0 instead.
Example 1:
Input: nums = [1,-1,5,-2,3], k = 3 Output: 4 Explanation: The subarray [1, -1, 5, -2] sums to 3 and is the longest.
Example 2:
Input: nums = [-2,-1,2,1], k = 1 Output: 2 Explanation: The subarray [-1, 2] sums to 1 and is the longest.
Constraints:
1 <= nums.length <= 104-104 <= nums[i] <= 104-105 <= k <= 105
Follow Up: Can you do it in O(n) time?