Data Structure

Array - 1D & 2D Arrays, Operations (Insertion, Deletion, Traversal), Subarrays & Prefix Sum

String - Basic Operations (Concatenation, Substring), String Manipulation Problems

Linked Lists - Singly & Doubly Linked Lists, Basic Operations (Insert, Delete, Reverse)

Stack & Queue - LIFO & FIFO Principles, Implementations (Array/Linked List), Applications (Parentheses Matching, BFS)

Hash Tables - Hashing Basics, Collision Handling (Chaining, Open Addressing), Frequency Counting Problems

Algorithm

Sorting Algorithms - Bubble, Selection, Insertion Sort, Merge Sort & Quick Sort (Divide & Conquer)

Searching Algorithms - Linear & Binary Search, Lower/Upper Bound (for sorted arrays)

Recursion - Basics (Factorial, Fibonacci), Backtracking (Permutations, Subsets)

Sliding Window - Fixed/Variable Size Window Problems, Example: Maximum Subarray Sum of Size k

Early Intermediate Topics

Binary Trees - Tree Traversals (Inorder, Preorder, Postorder), Level Order Traversal (BFS), Basic Problems (Height, Diameter)

Binary Search Trees (BST) - Insert/Search/Delete, Inorder Successor/Predecessor

Heaps (Priority Queues) - Min-Heap & Max-Heap, Heapify Algorithm, Top-K Elements Problem

Graph Basics - Representations (Adjacency List/Matrix), BFS & DFS Traversals, Cycle Detection (Undirected/Directed Graphs)

Greedy Algorithms - Activity Selection, Fractional Knapsack, Coin Change Problem (Greedy vs DP)

Dynamic Programming (Intro) - Memoization vs Tabulation, Classic Problems (Fibonacci, Climbing Stairs)

Problem-Solving Techniques

Two Pointers - Pair Sum, Remove Duplicates

Prefix Sum & Suffix Sum - Range Sum Queries

Bit Manipulation - Basic Operations (AND/OR/XOR), Counting Set Bits

Math for DSA - Prime Numbers, GCD/LCM, Modulo Arithmetic