DSA Roadmap

Learn DSA step by step — 124 free lessons with spaced repetition and active recall on RetainHQ, so what you study actually sticks.

Lessons

• 0/1 Knapsack
• 2D Arrays & Matrices
• Amortized Analysis
• Anagrams
• Arrays & Memory
• Backtracking template
• Base case
• BFS on graphs
• Big-O Notation
• Binary heap
• Binary Search on the Answer
• Binary Search
• Binary tree & traversals
• Bitmask DP
• Bitwise operators
• Brute force first
• BST: insert & search
• Bubble Sort
• Climbing stairs / Fibonacci
• Coin change
• Collisions & Load Factor
• Combination sum
• Combinatorics & counting
• Common Complexities
• Connected Components
• Counting bits
• Counting Operations
• Cycle Detection
• Designing data structures
• DFS on Graphs
• DFS: pre / in / post
• Difference array
• Dijkstra's Algorithm
• Edit distance
• Fast & slow pointers
• Fenwick tree (BIT)
• Find the middle
• Floyd's cycle detection
• Frequency Arrays
• Frequency Counting
• GCD, LCM & modular arithmetic
• Graph representations
• Grid DP (unique paths / min path sum)
• Hash Sets vs Maps
• Hash Tables
• Heap sort
• Height & diameter
• House robber
• In-Place Operations
• Insertion Sort
• Interval scheduling
• Iteration & Traversal
• Jump game
• Kadane's algorithm
• Level-order (BFS)
• Linear Search
• Linked list rewiring
• Logarithms & Powers of Two
• Longest common subsequence
• Longest increasing subsequence
• Lower Bound
• Lowest common ancestor
• Memoization (top-down)
• Merge intervals
• Merge Sort
• Merge two sorted lists
• Min stack
• Minimum Spanning Tree (Kruskal)
• Monotonic deque
• Monotonic stack
• N-Queens
• Next greater element
• Non-comparison sorts
• Optimal substructure
• Ordered sets & sorted containers
• Overlapping subproblems
• Palindromes
• Pattern Matching (KMP)
• Pattern recognition drill
• Permutations
• Precomputation
• Prefix Sums
• Queue & deque
• Quickselect
• Quicksort & partition
• Recognizing divide & conquer
• Recognizing graph problems
• Recognizing greedy vs DP
• Recognizing sliding window
• Recognizing two pointers
• Recursion tree
• Recursive relation
• Recursive tree thinking
• Reverse in k-groups
• Rolling hash (Rabin-Karp)
• Segment tree
• Selection Sort
• Single number (XOR)
• Sliding window (fixed)
• Sliding window (variable)
• Space optimization
• Stack fundamentals
• State & transition
• String Traversal
• Subsets
• Tabulation (bottom-up)
• The call stack
• Top-K with a heap
• Topological Sort
• Tracing State & Loop Invariants
• Traversal & reversal
• Tree DP
• Trie (prefix tree)
• Two Pointers on Strings
• Two pointers
• Union-Find
• Upper Bound
• Valid parentheses
• Validate a BST
• Weighted vs unweighted
• What is an Algorithm?
• When BFS Stops Working
• Why greedy fails
• Why greedy works