Given an array nums and a target value k, find the maximum length of a subarray that sums to k. If there isn't one, return 0 instead.
Example 1: Given nums = [1, -1, 5, -2, 3], k = 3, return 4. (because the subarray [1, -1, 5, -2] sums to 3 and is the longest)
Example 2: Given nums = [-2, -1, 2, 1], k = 1, return 2. (because the subarray [-1, 2] sums to 1 and is the longest)
Follow Up: Can you do it in O(n) time?
bruteforce n^2, use a memoized greedy algorithm
- to get the longest subarray matching a condition, the start_index is better be small
- use hashmap to maintain achieved lengths and values