misc. thoughts and maybe tips

libraries:
- essentials: bits/stdc++.h, iostream
- data structures: vector
(q21)when working with structs, can't return locally created objects from a function, even when using new keyword...?
2sum, 3sum, palindrome, and other two pointer problems can prolly be identified by how they require comparison-based solutions across the entire array, and the array is to be sorted or ordered in some way for traversal