15-3sum

3 sum

https://leetcode.com/problems/3sum/

1. Two Pointers

Time complexity: O(n*n) Space complexity: O(n)

2. Hashset

Time complexity: O(n*n) Space complexity: O(n)

1. No sort

Time complexity: O(n*n) Space complexity: O(n)

While the asymptotic complexity is the same, this algorithm is noticeably slower than the previous approach. Lookups in a hashset, though requiring a constant time, are expensive compared to the direct memory access.