Given aContinue reading “[Leetcode]222. Count Complete Tree Nodes”completebinary tree, count the number of nodes.Note:In a complete binary tree every level, except possibly the last, is completely filled, and all nodes in the last level are as far left as possible. It can have between 1 and 2Definition of a complete binary tree from Wikipedia:^{h}nodes inclusive at the last level h.Example:Input:1 / \ 2 3 / \ / 4 5 6Output:6

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

Question: Given a preorder traversal, reconstruct the binary search tree and return the root. Input:Continue reading “[Leetcode]1008. Construct Binary Search Tree from Preorder Traversal”`[8,5,1,7,10,12]`

Output:`[8,5,10,1,7,null,12]`

Visiualization of the output:

## [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.

Continue reading “[Leetcode for Interviews] BinaryTree Traversal – DFS & BFS”## 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.

Continue reading “Tree Traversal – Recursively & Iteratively”