This method of depth-first traversal is also known as preorder traversal. Once we're done, we will have visited the nodes in the following order: So how would we go about building this in code? Well ...

# Definition for a binary tree node.

There are three main ways to traverse a binary search tree: in-order, pre-order, and post-order. Each method has its own advantages and disadvantages depending on the problem you're trying to solve.