preorder Archives

May 27, 2020June 26, 2020

[Leetcode]1008. Construct Binary Search Tree from Preorder Traversal

Question:
Given a preorder traversal, reconstruct the binary search tree and return the root.

Input: [8,5,1,7,10,12]
Output: [8,5,10,1,7,null,12]
Visiualization of the output:

May 26, 2020June 20, 2020

[Leetcode for Interviews] BinaryTree Traversal – DFS & BFS

After introducing traversing trees using BFS and DFS in Tree Traversal – Recursively & Iteratively – Preorder, Inorder, Postorder, it’s time to get some practices! Here are Leetcode questions that appear frequently during tech interviews.

May 24, 2020July 9, 2020

Tree Traversal – Recursively & Iteratively

Tree traversal refers to the process of visiting each node in a tree data structure (Wikipedia). The two general strategies are Depth-First-Search (DFS) and Breadth-First-Search (BFS). For BFS, it iterates through the tree level by level with Queue, from top to bottom. When using DFS, there are three different ways: Preorder, Inorder, and Postorder.