Welcome to the leetcode series. If you're new to programming, solving basic programming challenges is a great way to get better. If you're practicing for a technical interview, using **leetcode** to rehearse is a famously way to get better.

In this series, we'll be walking through problems that you might see at coding interview challenges at such places as `AWS`

, `Meta`

, and `Google`

.

Check out all the solutions on github at: https://github.com/auser/leetcode.

- Longest Valid Parentheses
The Longest Valid Parentheses challenge

- Lowest common ancestor of a binary tree
Given a binary tree, find the lowest common ancestor (LCA) of two given nodes in the tree.

- Three sum closest
ThreeSum closest problem

- ThreeSum
ThreeSum problem

- Swap pairs in place
Swap pairs in-place with a singly linked list