Unit

Data Structure and Algorithm III

Master Advanced Data Structures & Algorithms: Trees, Backtracking, Tries, Heaps – Practice with Curated LeetCode Questions

Trees

Binary Tree

Binary Search Tree

Trie

Heap / Priority Queue

Backtracking

Duration

5 weeks

Introduction

Welcome to Data Structures and Algorithms III, where you'll conquer four advanced pillars of efficient problem-solving: Trees, Backtracking, Tries, and Heaps. This unit transforms these sophisticated concepts into practical skills through curated LeetCode challenges, replicating real-world system design and coding interviews.

You'll master binary/AVL trees for hierarchical data, backtracking for combinatorial problems, trie structures for text processing, and heaps for priority-driven algorithms – all while developing the pattern recognition needed to optimize solutions. Each concept is paired with targeted problems to bridge theory and implementation, preparing you to tackle everything from database indexing to algorithm optimization with confidence.

Prerequisites

Complete Data Structure and Algorithm II Unit.

Skills Covered

In this unit, we are going to cover the following topics.

Trees: Master traversals, BST operations, and balanced trees for hierarchical data efficiency.

Tries: Build prefix-based systems (autocomplete, spell check) with optimized string operations.

Heaps: Implement priority queues for real-time scheduling and top-K element retrieval.

Backtracking: Solve combinatorial problems (permutations, N-Queens) with recursive pruning.

Recommended Study Material

Trees

Learn the basics of Tree data structure and its implementation.

Trees

Binary Tree

Binary Search Tree

Data Structure

Duration:

1 hour

Trie

Learn the basics of Trie data structure and its implementation.

Trie

Data Structure

Duration:

1 hour

Heaps

Learn the basics of Heaps data structure and its implementation.

Heap

Min Heap

MaxHeap

Data Structure

Duration:

1 hour

Backtracking

Master the backtracking problem and solve two LeetCode hard problems in this crash course.

Backtracking

Algorithm

Duration:

2 hours

Practice Problems

Status	Bookmark	Problem	Difficulty	Tags	Solution
		Binary Tree Inorder Traversal	Easy
		Binary Tree Preorder Traversal	Easy
		Binary Tree Postorder Traversal	Easy
		Invert Binary Tree	Easy
		Maximum Depth of Binary Tree	Easy
		Diameter of Binary Tree	Easy
		Balanced Binary Tree	Easy
		Same Tree	Easy
		Subtree of Another Tree	Easy
		Lowest Common Ancestor of a Binary Search Tree	Medium
		Binary Tree Zigzag Level Order Traversal	Medium
		Binary Tree Level Order Traversal	Medium
		Binary Tree Right Side View	Medium
		Construct Quad Tree	Medium
		Count Good Nodes in Binary Tree	Medium
		Construct Binary Tree from Preorder and Inorder Traversal	Medium
		Delete Leaves With a Given Value	Medium
		Flatten Binary Tree to Linked List	Medium
		Binary Tree Maximum Path Sum	Hard
		Serialize and Deserialize Binary Tree	Hard
		Binary Tree to DLL	Hard
		Search in a Binary Search Tree	Easy
		Insert into a Binary Search Tree	Medium
		Validate Binary Search Tree	Medium
		Kth Smallest Element in a BST	Medium
		Delete Node in a BST	Medium
		Trim a Binary Search Tree	Medium
		My Calendar I	Medium
		My Calendar II	Medium
		Longest Common Prefix	Easy
		Implement Trie (Prefix Tree)	Medium
		Design Add and Search Words Data Structure	Medium
		Extra Characters in a String	Medium
		Word Search	Medium
		Word Search II	Hard
		Kth Largest Element in a Stream	Easy
		Last Stone Weight	Easy
		Take Gifts From the Richest Pile	Easy
		K Closest Points to Origin	Medium
		Kth Largest Element in an Array	Medium
		Task Scheduler	Medium
		Design Twitter	Medium
		Single-Threaded CPU	Medium
		Reorganize String	Medium
		Longest Happy String	Medium
		Car Pooling	Medium
		Split Array into Consecutive Subsequences	Medium
		Design a Food Rating System	Medium
		Stock Price Fluctuation	Medium
		Find Median from Data Stream	Hard
		IPO	Hard
		The Skyline Problem	Hard
		Sum of All Subset XOR Totals	Easy
		Subsets	Medium
		Combination Sum	Medium
		Combination Sum II	Medium
		Combinations	Medium
		Permutations	Medium
		Subsets II	Medium
		Permutations II	Medium
		Palindrome Partitioning	Medium
		Letter Combinations of a Phone Number	Medium
		Matchsticks to Square	Medium
		Partition to K Equal Sum Subsets	Medium
		N-Queens	Hard
		N-Queens II	Hard
		Sudoku Solver	Hard

Credit

The problem set is carefully curated from Neetcode and AlgoMaster, supplemented with additional practice questions for comprehensive coverage.

Contributor(s)

John Doe

Founder and Fullstack Developer at freeCodeProject.org

Created this Unit with curated list of questions for practice.