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Mastering Data Structures and Algorithms in Java: From Big O to Interview Success

Master essential data structures and algorithms in Java to ace technical coding interviews. Learn Big O complexity, dynamic programming, trees, graphs, and algorithmic patterns through comprehensive problem-solving techniques.

freeCodeCamp.org
freeCodeCamp.org@freecodecamp
Published Oct 9, 2026
Updated Oct 13, 2026
Mastering Data Structures and Algorithms in Java: From Big O to Interview Success
49h 44m
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Course Overview

This in-depth curriculum delivers an exhaustive foundation in computer science fundamentals, data structures, and algorithmic problem-solving using Java. Designed specifically for software engineers preparing for competitive technical interviews, the course transitions from computational complexity theory into hands-on implementation and algorithmic pattern recognition.

What You'll Learn

  • Complexity Analysis: Evaluate runtime and memory overhead using Big O, Big Omega, and Big Theta notations.
  • Linear Data Structures: Build and manipulate dynamic arrays, linked lists, stacks, and queues from first principles.
  • Non-Linear Structures: Traverse and balance binary trees, binary search trees (BST), heaps, tries, and disjoint-set unions (Union-Find).
  • Graph Theory: Implement Breadth-First Search (BFS), Depth-First Search (DFS), Dijkstra's shortest path, and topological sorting.
  • Advanced Problem-Solving: Formulate optimal subproblems with Dynamic Programming (memoization and tabulation), greedy heuristics, and backtracking.
  • Interview Patterns: Recognize and execute two-pointer, sliding window, interval scheduling, bitwise manipulation, and fast-and-slow pointer techniques.

Pattern Spotlight: Two-Pointer Traversal

public class TwoPointerSearch {
    // O(n) time complexity and O(1) auxiliary space
    public static boolean hasTargetSum(int[] sortedArray, int target) {
        int left = 0;
        int right = sortedArray.length - 1;
        while (left < right) {
            int sum = sortedArray[left] + sortedArray[right];
            if (sum == target) {
                return true;
            } else if (sum < target) {
                left++;
            } else {
                right--;
            }
        }
        return false;
    }
}

Prerequisites

  • Working knowledge of basic programming fundamentals and core Java syntax (variables, control flow, methods, and classes).
  • Foundational familiarity with basic high-school algebra and discrete mathematics concepts.

Tools & Technologies

  • Programming Language: Java (JDK 17+ recommended)
  • Development Environment: IntelliJ IDEA, Eclipse, or Visual Studio Code
  • Version Control: Git and GitHub for tracking problem solutions and implementations

Course Content

9Chapters26Lessons9Quizzes
1

Algorithmic Complexity and Technical Interview Fundamentals

3 lessons · 50mQuiz
1

Technical Interviews 101: Structure, Mindset, and Communication

7:02
2

Mastering Big O Notation and Code Block Time Complexity Analysis

26:06
3

Space Complexity Analysis and Core Data Structure Taxonomies

17:13
2

Array Manipulation, Two Pointers, and Sliding Window

3 lessons · 6h 10mQuiz
1

Mastering Array Fundamentals and In-Place Manipulation

158:41
2

Implementing Fixed and Dynamic Sliding Window Algorithms

100:46
3

Solving Complex Problems with Two-Pointer Strategies

110:37
3

String Algorithms, Sorting, and Binary Search

2 lessons · 4h 28mQuiz
1

Mastering String Manipulation and Pattern Matching in Java

89:02
2

Classical Sorting Algorithms and Binary Search Optimization

179:21
4

Linked Lists, Stacks, Queues, and Priority Queues

4 lessons · 9h 27mQuiz
1

Mastering Linked Lists: Pointer Manipulation, Reversal, and Cycle Detection

160:00
2

Stack Fundamentals: Monotonic Stacks, Expression Evaluation, and LIFO Patterns

155:07
3

Queues and Double-Ended Queues: FIFO Processing and Buffer Architectures

74:13
4

Priority Queues and Binary Heaps: Custom Comparators and Top-K Selection

177:46
5

Tree Structures and Binary Search Trees

3 lessons · 4h 24mQuiz
1

Tree Fundamentals and Depth-First Traversal Strategies

86:40
2

Breadth-First Search, Level-Order Traversal, and Tree Metrics

88:20
3

Binary Search Tree Operations, Validation, and Lowest Common Ancestor

89:07
6

Graph Algorithms and Traversal Strategies

3 lessons · 6h 54mQuiz
1

Graph Representations and Fundamental Traversals: BFS and DFS

138:04
2

Cycle Detection, Topological Sort, and Kahn's Algorithm

138:04
3

Shortest Path Algorithms and Disjoint Set Union (Union-Find)

138:04
7

Dynamic Programming and Greedy Paradigms

2 lessons · 6h 52mQuiz
1

Mastering Dynamic Programming: Memoization, Tabulation, and State Transitions

298:51
2

Greedy Algorithms: Optimal Substructure and Local Choice Heuristics

113:32
8

Backtracking, Intervals, and Matrix Manipulation

3 lessons · 6h 48mQuiz
1

Mastering Interval Patterns: Merging, Insertion, and Overlap Resolution

86:03
2

Combinatorial Backtracking: State Space Trees, Subsets, and Pruning Strategies

189:51
3

Matrix Traversal and In-Place Two-Dimensional Transformations

132:36
9

Bit Manipulation, Mathematical Algorithms, and Object-Oriented Design

3 lessons · 3h 49mQuiz
1

Solving Mathematical and Geometric Problems in Java

56:39
2

Designing Object-Oriented Systems and Interview Data Structures

87:27
3

Mastering Bit Manipulation and Low-Level Binary Logic

85:44
PriceFree
LanguageEnglish
XP29850
This course includes
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