DSA with Java Training Topic-Wise Online Mock Tests & Free MCQ Practice
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DSA with Java Training — Topic-Wise Mock Tests
Expand any module below to start a live timed MCQ exam across 244 Mock Test sets (max 2 free attempts per topic per day).
All Modules & Topics in DSA with Java Training
DSA Foundations in Java — ADTs vs Implementations, Primitive Cache Locality & Judge Constraints
Purpose: To understand and apply DSA Foundations in Java — ADTs vs Implementations, Primitive Cache Locality & Judge Constraints in real DSA with Java systems — specifically: Why choosing the right data structure turns a 10-second Time-Limit-Exceeded (`TLE`) brute-force loop into a 4ms optimal pass, and why `int[]` beats `ArrayList<Integer>` by 4–5x in memory and cache speed, so your code stays reliable, fast, and easy to maintain in production.
Asymptotic Notation — Big-O (`O`), Big-Omega (`Ω`), Big-Theta (`Θ`) & Amortized Analysis
Purpose: To understand and apply Asymptotic Notation — Big-O (`O`), Big-Omega (`Ω`), Big-Theta (`Θ`) & Amortized Analysis in real DSA with Java systems — specifically: Formal growth-rate bounds (`O(1) < O(log N) < O(N) < O(N log N) < O(N^2) < O(2^N)`), dropping constants and lower-order terms, harmonic series `O(N log N)` loops, and `ArrayList` `O(1)` amortized doubling, so your code stays reliable, fast, and easy to maintain in production.
Arrays in Java — `base + i * stride` Random Access, 3-Step Rotation & Two-Pointer Technique
Purpose: To understand and apply Arrays in Java — `base + i * stride` Random Access, 3-Step Rotation & Two-Pointer Technique in real DSA with Java systems — specifically: Understand why array indexing `arr[i]` is strictly `O(1)` while middle insertion/deletion costs `O(N)` `System.arraycopy` shifts, and solve classic in-place array problems with Two Pointers, so your code stays reliable, fast, and easy to maintain in production.
Singly Linked List — Pointer Rewiring, Sentinel Dummy Head, Floyd’s Cycle & In-Place Reversal
Purpose: To understand and apply Singly Linked List — Pointer Rewiring, Sentinel Dummy Head, Floyd’s Cycle & In-Place Reversal in real DSA with Java systems — specifically: Master dynamic node chains (`val`, `next`): `O(1)` head prepend, why random access is `O(N)`, iterative `prev/curr/next` pointer reversal, and Floyd’s Tortoise & Hare cycle detection, so your code stays reliable, fast, and easy to maintain in production.
Doubly Linked List — `prev`/`next` Sentinel Splicing, `O(1)` Node Deletion & LRU Cache Design
Purpose: To understand and apply Doubly Linked List — `prev`/`next` Sentinel Splicing, `O(1)` Node Deletion & LRU Cache Design in real DSA with Java systems — specifically: Why storing both `prev` and `next` unlocks `O(1)` deletion given a node reference (impossible in `O(1)` on tail nodes of a Singly Linked List!), making Doubly Linked Lists + `HashMap` the backbone of `O(1)` LRU Caches, so your code stays reliable, fast, and easy to maintain in production.
Stack in Java — LIFO `ArrayDeque` vs Legacy `Stack`, Balanced Brackets & `O(N)` Monotonic Stack
Purpose: To understand and apply Stack in Java — LIFO `ArrayDeque` vs Legacy `Stack`, Balanced Brackets & `O(N)` Monotonic Stack in real DSA with Java systems — specifically: Implement LIFO stacks with `Deque<Integer> st = new ArrayDeque<>()`, understand why `java.util.Stack` (extending synchronized `Vector`) is an anti-pattern, and master `O(N)` Monotonic Decreasing/Increasing Stacks, so your code stays reliable, fast, and easy to maintain in production.
Circular Queue (Ring Buffer) — Modulo Wrap-Around `(idx + 1) % k` & Full vs Empty Disambiguation
Purpose: To understand and apply Circular Queue (Ring Buffer) — Modulo Wrap-Around `(idx + 1) % k` & Full vs Empty Disambiguation in real DSA with Java systems — specifically: Why a naive array queue runs out of space after `N` dequeues even when empty, and how a **Circular Queue (Ring Buffer)** reuses freed front slots in `O(1)` time for producer-consumer buffers and networking rings, so your code stays reliable, fast, and easy to maintain in production.
Double-Ended Queue (`Deque`) — `offerFirst`/`offerLast`, 0-1 BFS & `O(N)` Sliding Window Maximum
Purpose: To understand and apply Double-Ended Queue (`Deque`) — `offerFirst`/`offerLast`, 0-1 BFS & `O(N)` Sliding Window Maximum in real DSA with Java systems — specifically: Push and pop from BOTH ends in `O(1)` time with `ArrayDeque`: unify Stack + Queue interfaces, solve 0-1 shortest paths without Dijkstra’s log factor, and compute Sliding Window Maximum in `O(N)`, so your code stays reliable, fast, and easy to maintain in production.
Hash Table & Java `HashMap` — `(h ^ (h >>> 16))`, Load Factor `0.75` & Red-Black `TreeNode`
Purpose: To understand and apply Hash Table & Java `HashMap` — `(h ^ (h >>> 16))`, Load Factor `0.75` & Red-Black `TreeNode` in real DSA with Java systems — specifically: How `HashMap` achieves `O(1)` average lookup and `O(log N)` worst-case bucket lookup (since Java 8’s `TREEIFY_THRESHOLD = 8` when `capacity >= 64`), Open Addressing vs Separate Chaining, and prefix-hash patterns, so your code stays reliable, fast, and easy to maintain in production.
Binary Search — Overflow-Safe Midpoint, Lower/Upper Bound & Binary Search on Answer
Purpose: To understand and apply Binary Search — Overflow-Safe Midpoint, Lower/Upper Bound & Binary Search on Answer in real DSA with Java systems — specifically: Go far beyond simple array lookup: master invariant-driven `lowerBound` (first index `>= target`), rotated sorted arrays, and **Binary Search on Answer** over any monotonic boolean predicate `canShip(capacity)`, so your code stays reliable, fast, and easy to maintain in production.
Merge Sort — Guaranteed `O(N log N)` Divide & Conquer, Stability (`<=`) & Inversion Counting
Purpose: To understand and apply Merge Sort — Guaranteed `O(N log N)` Divide & Conquer, Stability (`<=`) & Inversion Counting in real DSA with Java systems — specifically: Recursively split arrays to base size 1 and merge sorted halves in linear time: understand `T(N) = 2T(N/2) + O(N) => Θ(N log N)`, single-buffer allocation, linked-list `O(1)`-space merge sort, and inversion counting, so your code stays reliable, fast, and easy to maintain in production.
Quick Sort — Lomuto vs Hoare vs 3-Way Dutch Flag Partitioning & Randomized Pivot Safety
Purpose: To understand and apply Quick Sort — Lomuto vs Hoare vs 3-Way Dutch Flag Partitioning & Randomized Pivot Safety in real DSA with Java systems — specifically: Understand why in-place Quick Sort beats Merge Sort on primitives via superior L1 cache locality, why naive `a[high]` pivots degrade to `O(N^2)` on sorted arrays, and how 3-Way partitioning crushes duplicates in `O(N)`, so your code stays reliable, fast, and easy to maintain in production.
Binary Tree — DFS Traversals, Level-Order BFS, `O(N)` Postorder Diameter & Lowest Common Ancestor
Purpose: To understand and apply Binary Tree — DFS Traversals, Level-Order BFS, `O(N)` Postorder Diameter & Lowest Common Ancestor in real DSA with Java systems — specifically: Master Binary Tree properties (Full, Complete, Perfect, Balanced; `2^h` leaves), Pre/In/Postorder + BFS Level-Order (`q.size()` snapshot per level), and single-pass `O(N)` postorder aggregation, so your code stays reliable, fast, and easy to maintain in production.
Binary Search Tree (BST) — Global Subtree Bounds, Sorted Inorder, Hibbard Delete & `TreeMap`
Purpose: To understand and apply Binary Search Tree (BST) — Global Subtree Bounds, Sorted Inorder, Hibbard Delete & `TreeMap` in real DSA with Java systems — specifically: Exploit the global BST ordering invariant (EVERY node in `left` `< node.val <` EVERY node in `right`), inorder sorted streaming, Hibbard inorder-successor deletion, and why unguarded BSTs degenerate to `O(N)` sticks, so your code stays reliable, fast, and easy to maintain in production.
AVL Tree — Balance Factor `{-1, 0, +1}`, LL/RR/LR/RL `O(1)` Rotations & `1.44 log2(N)` Height Bound
Purpose: To understand and apply AVL Tree — Balance Factor `{-1, 0, +1}`, LL/RR/LR/RL `O(1)` Rotations & `1.44 log2(N)` Height Bound in real DSA with Java systems — specifically: How Adelson-Velsky & Landis (AVL) trees enforce `|height(L) - height(R)| <= 1` at every node via `O(1)` pointer rotations, guaranteeing `O(log N)` worst-case search even under adversarial sorted insertions, so your code stays reliable, fast, and easy to maintain in production.
Binary Heap & Java `PriorityQueue` — `O(N)` Floyd Heapify, Top-`K` Min-Heap & `Integer.compare`
Purpose: To understand and apply Binary Heap & Java `PriorityQueue` — `O(N)` Floyd Heapify, Top-`K` Min-Heap & `Integer.compare` in real DSA with Java systems — specifically: Understand Complete Binary Tree array indexing, why bottom-up Floyd `buildHeap` runs in linear `O(N)` (not `O(N log N)`!), and why finding the **`K` Largest** elements uses a **Min-Heap** of size `K` in `O(N log K)`, so your code stays reliable, fast, and easy to maintain in production.
Breadth-First Search (BFS) — Unweighted Shortest Path, Multi-Source BFS & Enqueue-Mark Rule
Purpose: To understand and apply Breadth-First Search (BFS) — Unweighted Shortest Path, Multi-Source BFS & Enqueue-Mark Rule in real DSA with Java systems — specifically: Explore graphs ring-by-ring in monotonic distance order (`dist = 0, 1, 2, ...`) using `ArrayDeque`: unweighted shortest paths, Bipartite 2-coloring, Word Ladder, and Multi-Source Grid BFS, so your code stays reliable, fast, and easy to maintain in production.
Depth-First Search (DFS) — Connected Components, 3-Color Directed Cycle Detection & Topological Sort
Purpose: To understand and apply Depth-First Search (DFS) — Connected Components, 3-Color Directed Cycle Detection & Topological Sort in real DSA with Java systems — specifically: Plunge along graph paths recursively or iteratively: flood-fill islands, classify back-edges via 3-color states (`0/1/2`) to detect DAG cycles, and emit reverse-postorder Topological Sorts, so your code stays reliable, fast, and easy to maintain in production.
Kruskal’s Algorithm & Disjoint Set Union — Cut Property, Path Compression & `O(E log E)` MST
Purpose: To understand and apply Kruskal’s Algorithm & Disjoint Set Union — Cut Property, Path Compression & `O(E log E)` MST in real DSA with Java systems — specifically: Sort all edges by ascending weight and greedily accept each edge `(u, v, w)` whose endpoints belong to distinct connected components via near-constant `O(α(V))` **Disjoint Set Union (Union-Find)**, so your code stays reliable, fast, and easy to maintain in production.
Prim’s Algorithm — Vertex-Cut Min-Heap Growth, Lazy `inMst` Filtering & Dense vs Sparse Choice
Purpose: To understand and apply Prim’s Algorithm — Vertex-Cut Min-Heap Growth, Lazy `inMst` Filtering & Dense vs Sparse Choice in real DSA with Java systems — specifically: Grow a single connected tree from an arbitrary start vertex `0` by repeatedly pulling the lightest frontier edge `(w, v)` from a `PriorityQueue` where `v` is not yet in the MST, so your code stays reliable, fast, and easy to maintain in production.
BFS/DFS State Modeling, Cycle Detection & Kahn’s Topological Sort
Purpose: To understand and apply BFS/DFS State Modeling, Cycle Detection & Kahn’s Topological Sort in real DSA with Java systems — specifically: Solve course-schedule, build-system order, and grid shortest-path interview problems, so your code stays reliable, fast, and easy to maintain in production.
Dijkstra (PriorityQueue), 0-1 BFS & Bellman-Ford Weighted Paths
Purpose: To understand and apply Dijkstra (PriorityQueue), 0-1 BFS & Bellman-Ford Weighted Paths in real DSA with Java systems — specifically: Compute minimum-cost network and delivery routes with optimal O((V+E) log V) Java code, so your code stays reliable, fast, and easy to maintain in production.
Disjoint Set Union (Path Compression + Union by Rank) & Kruskal MST
Purpose: To understand and apply Disjoint Set Union (Path Compression + Union by Rank) & Kruskal MST in real DSA with Java systems — specifically: Answer dynamic connectivity and clustering queries in near-constant O(alpha(N)) time, so your code stays reliable, fast, and easy to maintain in production.
Multi-Source BFS & Bipartite Graph Coloring
Purpose: To understand and apply Multi-Source BFS & Bipartite Graph Coloring in real DSA with Java systems — specifically: Tackle rotten-oranges, flood-spread, and conflict-partitioning FAANG graph rounds, so your code stays reliable, fast, and easy to maintain in production.
Top-Down Memoization -> Bottom-Up Tabulation -> Space Optimization
Purpose: To understand and apply Top-Down Memoization -> Bottom-Up Tabulation -> Space Optimization in real DSA with Java systems — specifically: Convert exponential O(2^N) recursion into crisp O(N*W) DP systematically every time, so your code stays reliable, fast, and easy to maintain in production.
0/1 & Unbounded Knapsack, Subset Sum & Coin-Change Pattern Family
Purpose: To understand and apply 0/1 & Unbounded Knapsack, Subset Sum & Coin-Change Pattern Family in real DSA with Java systems — specifically: Recognize capacity-allocation problems immediately in OA coding assessments, so your code stays reliable, fast, and easy to maintain in production.
LCS, Edit Distance, LIS (O(N log N) Patience) & Palindromic DP
Purpose: To understand and apply LCS, Edit Distance, LIS (O(N log N) Patience) & Palindromic DP in real DSA with Java systems — specifically: Master string/subsequence DP asked across Amazon, Google, and Microsoft interviews, so your code stays reliable, fast, and easy to maintain in production.
Interval DP, DP on Trees & State-Machine Stock Trading Problems
Purpose: To understand and apply Interval DP, DP on Trees & State-Machine Stock Trading Problems in real DSA with Java systems — specifically: Handle cooldown/transaction-capped trading and tree diameter/robber rounds confidently, so your code stays reliable, fast, and easy to maintain in production.
Prefix Tries & Bitwise XOR Tries
Purpose: To understand and apply Prefix Tries & Bitwise XOR Tries in real DSA with Java systems — specifically: Power O(L) search autocomplete, spellcheck, and maximum-XOR subarray queries, so your code stays reliable, fast, and easy to maintain in production.
Fenwick Tree (BIT) & Segment Tree with Point Update / Range Query
Purpose: To understand and apply Fenwick Tree (BIT) & Segment Tree with Point Update / Range Query in real DSA with Java systems — specifically: Maintain live prefix sums and range minimums across millions of streaming updates, so your code stays reliable, fast, and easy to maintain in production.
Rolling Hash (Rabin-Karp), KMP Prefix Function & Z-Algorithm
Purpose: To understand and apply Rolling Hash (Rabin-Karp), KMP Prefix Function & Z-Algorithm in real DSA with Java systems — specifically: Match substrings in strict linear O(N + M) time without worst-case quadratic TLEs, so your code stays reliable, fast, and easy to maintain in production.
Sweep-Line Intervals, Difference Arrays & Coordinate Compression
Purpose: To understand and apply Sweep-Line Intervals, Difference Arrays & Coordinate Compression in real DSA with Java systems — specifically: Count peak concurrent meetings/servers cleanly over large timestamp ranges, so your code stays reliable, fast, and easy to maintain in production.
Monotonic Stack & Deque (Sliding Window Max, Largest Histogram)
Purpose: To understand and apply Monotonic Stack & Deque (Sliding Window Max, Largest Histogram) in real DSA with Java systems — specifically: Turn brute-force O(N*K) window/span problems into single-pass O(N) solutions, so your code stays reliable, fast, and easy to maintain in production.
Heap Design Patterns: Two-Heaps Median, K-Way Merge & Top-K Frequent
Purpose: To understand and apply Heap Design Patterns: Two-Heaps Median, K-Way Merge & Top-K Frequent in real DSA with Java systems — specifically: Stream live medians and merge sorted shards using Java PriorityQueue, so your code stays reliable, fast, and easy to maintain in production.
Doubly-Linked + HashMap O(1) LRU/LFU Cache & Token-Bucket Rate Limiter
Purpose: To understand and apply Doubly-Linked + HashMap O(1) LRU/LFU Cache & Token-Bucket Rate Limiter in real DSA with Java systems — specifically: Ace the most frequent SDE-1/SDE-2 low-level machine-coding interview rounds, so your code stays reliable, fast, and easy to maintain in production.
Complexity Trade-Off Communication & Edge-Case Dry-Run Protocol
Purpose: To understand and apply Complexity Trade-Off Communication & Edge-Case Dry-Run Protocol in real DSA with Java systems — specifically: Verbalize invariants, Big-O bounds, and integer-overflow guards like a top 5% candidate, so your code stays reliable, fast, and easy to maintain in production.
Prefix Tries, Bitwise XOR Tries & String Rolling-Hash / KMP Pattern Matching
Purpose: To understand and apply Prefix Tries, Bitwise XOR Tries & String Rolling-Hash / KMP Pattern Matching in real DSA with Java systems — specifically: Solve dictionary search, IP routing, and linear-time substring problems in O(L) / O(N) time, so your code stays reliable, fast, and easy to maintain in production.
Disjoint Set Union (Union-Find with Path Compression), Bridges & Topological Cycles
Purpose: To understand and apply Disjoint Set Union (Union-Find with Path Compression), Bridges & Topological Cycles in real DSA with Java systems — specifically: Detect dynamic network connectivity, dependency deadlocks, and minimum spanning trees rapidly, so your code stays reliable, fast, and easy to maintain in production.
Segment Trees, Fenwick (BIT) Trees & Monotonic Queue/Stack Optimization
Purpose: To understand and apply Segment Trees, Fenwick (BIT) Trees & Monotonic Queue/Stack Optimization in real DSA with Java systems — specifically: Drop range-sum/min updates from O(N) to O(log N) and sliding-window extrema to O(N), so your code stays reliable, fast, and easy to maintain in production.
Recognizing Patterns Instantly: Mapping Problem Constraints (N <= 10^5) to Exact Big-O Targets
Purpose: To understand and apply Recognizing Patterns Instantly: Mapping Problem Constraints (N <= 10^5) to Exact Big-O Targets in real DSA with Java systems — specifically: Choose between DP, Greedy, Binary Search on Answer, or Two Pointers within 2 minutes of reading a prompt, so your code stays reliable, fast, and easy to maintain in production.
Integer Overflow Guards, Off-by-One Invariants & Iterative Stack Conversions in Java
Purpose: To understand and apply Integer Overflow Guards, Off-by-One Invariants & Iterative Stack Conversions in Java in real DSA with Java systems — specifically: Eliminate StackOverflowError and long-overflow WA failures on adversarial hidden test cases, so your code stays reliable, fast, and easy to maintain in production.
Communicating Brute-Force -> Optimal Trade-Offs Aloud in Live SDE Interviews
Purpose: To understand and apply Communicating Brute-Force -> Optimal Trade-Offs Aloud in Live SDE Interviews in real DSA with Java systems — specifically: Structure dry runs, complexity proofs, and clean modular Java helper methods under time pressure, so your code stays reliable, fast, and easy to maintain in production.