BSc CSIT DSA Important Questions (CSC211): Chapter-wise Past Papers, Repeated Questions & Exam Guide (TU)
Introduction
DSA has a reputation for being the hardest 3rd-semester subject. Talk to students who failed it and you'll usually hear one of two explanations: they tried to memorize algorithms without understanding them, or they studied everything equally and ran out of time before the exam. Both are avoidable problems.
The first is solved by your notes and practice. The second is solved by knowing what TU actually asks.
This guide is not a set of complete notes. If you need chapter-wise explanations, algorithms, C programs, and complexity analysis, that's all in the Complete BSc CSIT DSA Notes (CSC211). What this guide does is different: it tells you which questions appear in TU exams year after year, which units carry the most marks, which algorithms you must be able to trace by hand, and how to spend your final revision week so you're not wasting time on topics that rarely appear.
TU DSA exam questions are more predictable than most students realize. The same BFS, BST, linked list, and quick sort questions appear across different papers in slightly different forms. If you've practiced those core patterns until they're automatic, a large portion of the exam becomes manageable — even if you've never seen the exact question before.
Official Course Information
| Particular | Details |
|---|---|
| Course Title | Data Structure and Algorithm |
| Course Code | CSC211 |
| Semester | Third Semester |
| Full Marks | 60 + 20 + 20 |
| Pass Marks | 24 + 8 + 8 |
| Theory Paper | 60 marks |
How TU Sets the DSA Theory Paper
Understanding the exam format before studying is more useful than most students realize. The 60-mark theory paper typically follows this structure:
Long questions (10 marks each): These require full algorithm explanation, step-by-step trace with given data, and often a diagram. Expect 4–5 long questions from units covering Trees, Graphs, Sorting, and Linked Lists. These units appear almost every year in long-answer form.
Short questions (5 marks each): Definitions, comparisons ("differentiate between X and Y"), small trace examples, or complexity analysis. Stack, Queue, ADT, recursion, and complexity notation (Big-O) dominate this section.
Numerical/trace questions: You're given a specific dataset and asked to trace an algorithm step by step — show each state of the data structure as the algorithm runs. BST construction, BFS/DFS traversal, quick sort partition, and infix-to-postfix conversion are the most commonly traced.
Exam Weightage by Unit
| Unit | Topic | Likely Question Type | Importance |
|---|---|---|---|
| Unit 1 | Introduction, ADT, Complexity | Short | ★★★☆☆ |
| Unit 2 | Stack | Short + Numerical (infix-postfix) | ★★★★☆ |
| Unit 3 | Queue | Short | ★★★☆☆ |
| Unit 4 | Recursion | Short + Write program | ★★★★☆ |
| Unit 5 | Lists (Linked List) | Long + Program | ★★★★★ |
| Unit 6 | Sorting | Long + Trace | ★★★★★ |
| Unit 7 | Searching + Hashing | Long + Numerical | ★★★★☆ |
| Unit 8 | Trees + Graphs | Long + Trace (2 questions likely) | ★★★★★ |
Unit 1: Introduction — Important Questions
Most Asked Long Questions
- Define Abstract Data Type (ADT). What is the difference between data type and data structure?
- Explain asymptotic notations O, Ω, and Θ with examples.
Frequently Asked Short Questions
- Differentiate between static and dynamic memory allocation.
- Define algorithm. What are the properties of a good algorithm?
- Differentiate between time complexity and space complexity.
- What is Big-O notation? Give examples of O(1), O(n), and O(n²).
Concepts You Must Understand
- ADT separates what a structure does from how it's implemented
- O(1) < O(log n) < O(n) < O(n log n) < O(n²) — know this order
- Dynamic memory allocation using
mallocin C
Exam probability: ★★★☆☆ | Usually 1 short question (5 marks)
Unit 2: Stack — Important Questions
Most Asked Long Questions
- Explain stack as an ADT. Write a C program for stack using array.
- Convert the infix expression
(A+B)*(C-D)/Eto postfix using stack. Show full trace. - Evaluate the postfix expression
523*+4-using stack. Show each step.
Frequently Asked Short Questions
- What is a stack? List its applications.
- Differentiate between stack and queue.
- Explain the push and pop operations.
Infix to Postfix — Practice This Until It's Automatic
This appears in almost every TU DSA exam. The key rules: output operands immediately; push operators to stack respecting precedence; pop on ) until matching (; pop everything at the end.
Expression to practice: A*(B+C)-D/E
Operator precedence (high to low): ^ → *, / → +, -
Exam probability: ★★★★☆ | Often 10-mark question or numerical
Unit 3: Queue — Important Questions
Most Asked Long Questions
- Explain circular queue. Why is it preferred over linear queue? Write C implementation.
- Compare linear queue, circular queue, priority queue, and deque.
Frequently Asked Short Questions
- What is the difference between stack and queue?
- Explain FIFO. Give examples where queue is used.
- What is a priority queue?
Concepts You Must Understand
- Linear queue wastes space — front can't be reused after dequeue
- Circular queue fixes this with
rear = (rear + 1) % MAX - Queue applications: CPU scheduling, BFS traversal, printer spooling
Exam probability: ★★★☆☆ | Usually 1 short question
Unit 4: Recursion — Important Questions
Most Asked Long Questions
- Write a recursive C program for Tower of Hanoi. Trace it for n=3, showing all moves.
- Explain recursion. Differentiate between recursion and iteration with examples.
- Write recursive programs for factorial and Fibonacci.
Frequently Asked Short Questions
- What is tail recursion?
- What is the base case in recursion? Why is it necessary?
- What is GCD? Write its recursive algorithm.
Tower of Hanoi — Always Write the Formula
For n disks, number of moves = 2ⁿ - 1. This is asked both as a question and as a derivation. n=3 → 7 moves. Write out all 7 moves in sequence when tracing.
Exam probability: ★★★★☆ | Tower of Hanoi trace comes up regularly
Unit 5: Lists (Linked List) — Important Questions
Most Asked Long Questions
- Write a C program to insert a node at the beginning, end, and specified position of a singly linked list.
- Write a C program to delete a node from a specified position in a singly linked list.
- Explain doubly linked list. Write insertion and deletion algorithms.
- Compare arrays and linked lists. When would you prefer one over the other?
- Explain how a stack can be implemented using a linked list.
Frequently Asked Short Questions
- Differentiate between singly and doubly linked list.
- What are the advantages of linked lists over arrays?
- What is a circular linked list?
Critical Code Pattern — Insertion at Beginning
struct Node* insertBeginning(struct Node* head, int data) {
struct Node* newNode = malloc(sizeof(struct Node));
newNode->data = data;
newNode->next = head;
return newNode;
}
Know this pattern cold. Variations (insert at end, insert at position) all follow the same pointer-update logic.
Exam probability: ★★★★★ | Long question with program is almost certain
Unit 6: Sorting — Important Questions
Most Asked Long Questions
- Explain quick sort with a step-by-step trace on [5, 3, 8, 4, 2, 7, 1, 6].
- Explain merge sort with a diagram. What is its time complexity?
- Write and explain insertion sort. Trace on [64, 34, 25, 12, 22].
- Compare all sorting algorithms: bubble, selection, insertion, merge, quick, heap — complexity table.
Frequently Asked Short Questions
- Why is quick sort's worst case O(n²)? When does it occur?
- What is a stable sorting algorithm? Which algorithms are stable?
- What is the difference between internal and external sorting?
Sorting Complexity — Memorize This Table
| Algorithm | Best | Average | Worst | Space |
|---|---|---|---|---|
| Bubble Sort | O(n) | O(n²) | O(n²) | O(1) |
| Selection Sort | O(n²) | O(n²) | O(n²) | O(1) |
| Insertion Sort | O(n) | O(n²) | O(n²) | O(1) |
| Merge Sort | O(n log n) | O(n log n) | O(n log n) | O(n) |
| Quick Sort | O(n log n) | O(n log n) | O(n²) | O(log n) |
| Heap Sort | O(n log n) | O(n log n) | O(n log n) | O(1) |
This table appears in multiple question forms. Know it so well you can write it in 30 seconds.
Exam probability: ★★★★★ | At least one sorting long question guaranteed
Unit 7: Searching and Hashing — Important Questions
Most Asked Long Questions
- Explain binary search with algorithm and trace on a given sorted array.
- Explain hashing. Describe collision resolution techniques: chaining and open addressing.
- What is a hash function? Explain the division method with examples.
Frequently Asked Short Questions
- Compare linear search and binary search.
- What is a collision in hashing? How is it resolved?
- When can binary search not be used?
Binary Search Trace — Practice Format
Always show as a table: Low | High | Mid | arr[mid] | Action. Examiners mark each step. A correct trace with a wrong final answer still earns partial marks; a correct final answer with no steps shown earns nothing.
Exam probability: ★★★★☆ | Binary search trace almost always appears
Unit 8: Trees and Graphs — Important Questions
This unit is the most heavily examined. Expect two questions from this unit in most TU papers — one on Trees (BST/AVL) and one on Graphs (BFS/DFS/Dijkstra).
Most Asked Long Questions — Trees
- Construct a BST by inserting the following keys in sequence: [50, 30, 70, 20, 40, 60, 80]. Show the tree at each step.
- Write in-order, pre-order, and post-order traversals of a given binary tree.
- What is an AVL tree? Explain balancing with LL, RR, LR, and RL rotations using examples.
- What is a heap? Explain heap sort.
Most Asked Long Questions — Graphs
- Explain BFS and DFS traversal. Apply both on a given graph starting from a given vertex.
- Explain Dijkstra's shortest path algorithm with a step-by-step trace on a weighted graph.
- Explain Kruskal's algorithm for minimum spanning tree. Trace on a given graph.
- Compare BFS and DFS: data structure used, traversal order, applications.
Frequently Asked Short Questions
- Differentiate between binary tree and BST.
- What is graph traversal? Name two methods.
- What is a spanning tree?
- Define: height of tree, leaf node, complete binary tree.
BST Inorder = Sorted Output — Always Mention This
When any BST question is asked, always state: "Inorder traversal of a BST gives elements in sorted ascending order." This is a consistent mark-earner that many students forget to write.
BFS Uses Queue, DFS Uses Stack — Never Mix These Up
This distinction is one of the most common careless errors in the exam. Write it in your answer even when not asked directly.
Exam probability: ★★★★★ | Almost certainly 2 long questions from this unit
Most Repeated Questions (5-Year Trend)
Asked 4 or More Times
- Infix to postfix conversion using stack (with trace)
- BST construction and traversals
- BFS and DFS on a given graph
- Quick sort trace with given data
- Linked list insertion/deletion (C program or algorithm)
- Binary search with trace table
Asked 2–3 Times
- Tower of Hanoi (n=3 trace)
- Circular queue explanation and implementation
- Merge sort with diagram
- AVL tree and rotations
- Heap sort
- Hashing and collision resolution (chaining vs open addressing)
- Dijkstra's shortest path
Occasionally Asked (Prepare as Short Notes)
- Prim's algorithm vs Kruskal's
- Shell sort
- Tail recursion
- Deque (double-ended queue)
Rarely Asked (Low Priority)
- External vs internal sorting details
- Dynamic memory allocation in depth
- Doubly circular linked list specifically
Important Algorithms — Quick Reference
| Algorithm | Time (Average) | Time (Worst) | What to Know |
|---|---|---|---|
| Linear Search | O(n) | O(n) | Works on unsorted; checks every element |
| Binary Search | O(log n) | O(log n) | Requires sorted input; halves search space |
| Bubble Sort | O(n²) | O(n²) | Compare adjacent pairs; stable |
| Quick Sort | O(n log n) | O(n²) | Pivot-based partition; not stable |
| Merge Sort | O(n log n) | O(n log n) | Divide and conquer; stable; needs O(n) space |
| BST Search | O(log n) avg | O(n) worst | Worst case = skewed tree |
| BFS | O(V+E) | O(V+E) | Uses queue; level-order |
| DFS | O(V+E) | O(V+E) | Uses stack/recursion; depth-first |
| Dijkstra | O(V²) | O(V²) | Non-negative weights only |
Viva Questions (Lab Exam)
The lab viva tests whether you understand the theory behind the code you submitted. Common viva questions:
- What is the difference between stack and queue?
- What is recursion? What happens without a base case?
- Define ADT. Give an example.
- What is Big-O notation?
- What is the difference between tree and graph?
- What data structure does BFS use? What about DFS?
- When would you use a linked list over an array?
- What is a balanced BST? Why do we need it?
- What is collision in hashing? How is it resolved?
- What is the difference between AVL tree and BST?
- What makes quick sort's worst case O(n²)?
- What is inorder traversal? What does it give for a BST?
Last-Week Revision Plan
If you have one week before the exam, here is how to use it without wasting time:
Day 1: Unit 5 (Linked List) — write insertion and deletion C programs from memory. Do not look at notes while writing. This is the most guaranteed long question.
Day 2: Unit 6 (Sorting) — trace bubble sort and quick sort with data. Write the complexity table from memory. Do merge sort diagram.
Day 3: Unit 8 Trees — build a BST from a given sequence. Write all three traversals. Draw AVL rotation diagrams.
Day 4: Unit 8 Graphs — trace BFS and DFS on a 6-node graph. Trace Dijkstra on a small weighted graph.
Day 5: Unit 2 (Stack) — practice infix-to-postfix conversion with 3 different expressions. Evaluate one postfix expression.
Day 6: Units 1, 3, 4, 7 — short questions only. Review complexity table. Practice binary search trace. Tower of Hanoi for n=3.
Day 7: Write out answers to the 10 most-repeated questions from the list above. No new material. Focus on diagram quality and step clarity.
Common Mistakes That Cost Marks
Not showing algorithm steps: In numerical questions, the steps earn marks, not just the final answer. A correct BST with no construction trace shown loses marks.
Mixing up BFS and DFS data structures: BFS = Queue. DFS = Stack. Writing the wrong one makes the rest of the answer inconsistent even if the logic is correct.
Quick sort worst case confusion: Students say O(n log n) for all cases. The worst case is O(n²) — when the pivot is always the smallest or largest element.
Forgetting inorder = sorted for BST: Always state this when writing BST answers. It demonstrates understanding and earns marks.
No diagram for tree questions: Tree questions without a diagram are treated as incomplete answers in TU exams. Draw the tree at every stage.
Wrong traversal order: Inorder is Left-Root-Right, Preorder is Root-Left-Right, Postorder is Left-Right-Root. Mixing these is one of the most common errors on paper.
Frequently Asked Questions
How many units does CSC211 have? Eight units: Introduction, Stack, Queue, Recursion, Lists, Sorting, Searching and Hashing, and Trees and Graphs.
Is DSA difficult in BSc CSIT 3rd Semester? The concepts are logical, but DSA requires practice more than most subjects — reading algorithms without tracing them through examples doesn't build the skill the exam tests.
Which chapter is most scoring? Trees and Graphs (Unit 8) and Lists (Unit 5) consistently generate the most long-question marks. Sorting (Unit 6) is also heavily weighted. Together these three units likely account for more than half the theory marks.
Are previous year questions repeated in TU DSA exams? Yes — not word-for-word, but the core patterns repeat. BST construction, infix-to-postfix, BFS/DFS trace, and linked list programs appear in different forms across multiple years.
How should I prepare DSA in one week? Follow the Last-Week Revision Plan above. Prioritize Units 5, 6, and 8. Don't try to cover everything equally — concentrate on the highest-probability topics.
How many programs should I practice? At minimum: singly linked list insertion and deletion, stack push/pop, circular queue, binary search, and BST insertion with traversal. Write each from memory at least twice.
Is hashing asked every year? It appears regularly as a long or short question — usually asking about hash functions, collision handling, or comparison of chaining vs open addressing. It's medium priority but consistent enough to prepare.
What is the most important algorithm in DSA for the exam? If forced to choose one, BST operations (insertion + traversals) — it appears in almost every paper and tests multiple concepts simultaneously.
Conclusion
Smart exam preparation for DSA is not about covering everything — it's about covering the right things deeply enough that you can trace an algorithm step by step under time pressure with unfamiliar data. The questions in this guide represent the patterns that have proven most durable across TU past papers.
Use this guide alongside the complete notes: Complete BSc CSIT Data Structures and Algorithms (CSC211) Guide has the full explanations, C programs, and chapter-wise content for everything listed here.
For related subjects: C Programming (CSC115) Complete Guide, Computer Networks (CSC263) Important Questions, Cryptography (CSC316) Complete Guide.
: Chapter-wise Past Papers, Repeated Questions & Exam Guide (TU)){kind=link}
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