DSA with Java – Complete Roadmap
Step 1: Master Java Basics
• Learn syntax & fundamentals:
o Variables, data types, operators
o Conditionals (if, switch)
o Loops (for, while)
o Arrays & Strings
• OOP Concepts:
o Classes and Objects
o Inheritance, Polymorphism
o Abstraction, Encapsulation
Resources:
• W3Schools Java
• Java Programming by Apna College (YouTube)
Step 2: Learn Time & Space Complexity
• Big O Notation
• Best, Average, Worst case
• Time complexities of common operations (in arrays, lists, etc.)
Step 3: Core DSA Concepts (with Java Implementation)
Arrays & Strings
• Basics, 2D arrays
• Sliding window, prefix sums
• String manipulation
• StringBuilder vs String
Linked Lists
• Singly, Doubly, Circular
• Reverse, detect loop
• Fast and slow pointer approach
Stacks and Queues
• Using arrays, LinkedList, Java's Stack & Queue
• Problems: Balanced parentheses, Next greater element
Recursion & Backtracking
• Base case and recursive case
• Subsets, permutations
• Sudoku solver, N-Queens
Hashing (HashMap, HashSet)
• Frequency count, HashMap tricks
• Anagrams, subarrays with sum
Trees and Binary Trees
• Traversals (inorder, preorder, postorder)
• Level order (BFS), DFS
• BST operations
• Lowest Common Ancestor (LCA), Diameter
Heaps / Priority Queues
• Java PriorityQueue
• Top K elements problems
Graphs
• Representation: Adjacency list/matrix
• BFS & DFS
• Dijkstra, Union-Find, Topo Sort
Tries
• Implementation with Java classes
• Autocomplete, prefix search
Dynamic Programming
• 1D and 2D DP
• Memoization vs Tabulation
• Classic problems: Knapsack, LIS, LCS, Matrix DP
Step 4: Solve Problems (Practice Platforms)
Platform For LeetCode Interviews & Practice
HackerRank
Learning + Problems
GeeksForGeeks
Theory + Practice
Codeforces / AtCoder
Competitive programming
Coding Ninjas Java DSA
Structured courses
Step 5: Patterns & Interview Prep
• Learn problem-solving patterns:
o Two pointers, sliding window, binary search
o Fast/slow pointer, BFS/DFS, Greedy
• Practice mock interviews on:
o InterviewBit
o Pramp
Step 6: Learn Java Collections Framework
• List, Set, Map
• PriorityQueue, Deque
• Comparator vs Comparable
• Use JCF in DSA solutions
