Computational Structures

Computer Science, HSSC-Punjab First Year. This chapter is split into 50 topics and has 1,216 practice questions. The topics covered are listed below, followed by 10 free sample questions from the chapter.

Topics in this chapter

1. Queue front and rear tracking 26 questions
2. List length membership and position 25 questions
3. Operations across structures 24 questions
4. Graph weights and route costs 26 questions
5. List definition and creation 20 questions
6. Graph versus tree 24 questions
7. List index access 27 questions
8. Choosing the suitable structure 23 questions
9. Directed graphs 24 questions
10. Stack and queue side by side 30 questions
11. Stack real-life examples 20 questions
12. Computational structures overview 22 questions
13. Choosing a stack or a queue 24 questions
14. Graph concept vertices and edges 23 questions
15. Tree versus list organization 20 questions
16. Tree levels descendants and siblings 28 questions
17. Graph neighbours and paths 30 questions
18. Stack size and top tracking 26 questions
19. Tree concept and structure 22 questions
20. List searching with in 25 questions
21. Exercise style multiple choice items 21 questions
22. List properties 21 questions
23. Weighted graphs 22 questions
24. Family tree example 22 questions
25. Stack concept and LIFO 23 questions
26. Undirected graphs 24 questions
27. Stack push-pop tracing 30 questions
28. List mixed operation sequences 25 questions
29. Queue enqueue-dequeue tracing 30 questions
30. Graph degree of a vertex 23 questions
31. Short and long question topics 23 questions
32. Balanced tree checks 26 questions
33. List remove by value 22 questions
34. List insert operation 25 questions
35. Tree height levels and counts 28 questions
36. Queue program in Python 25 questions
37. Balanced trees 21 questions
38. Tree traversal orders 30 questions
39. Queue enqueue and dequeue operations 24 questions
40. List append and length 24 questions
41. Tree terms root node edge leaf 22 questions
42. List pop by index 25 questions
43. Stack versus queue comparison 24 questions
44. Tree applications 22 questions
45. Queue concept and FIFO 23 questions
46. Stack push and pop operations 23 questions
47. Graph applications and examples 21 questions
48. Directed graph in and out edges 28 questions
49. List applications and shared references 24 questions
50. Stack program in Python 26 questions

Sample questions: Computational Structures

10 sample questions with the correct answer and an explanation. Try to answer each one before reading the explanation.

Q1. push blue plate, push glass plate, push green plate, push steel plate, push white plate, pop, pop: these operations are applied in order to an empty stack. Which list shows the stack from bottom to top at the end?

• A. ['blue plate', 'glass plate', 'green plate'](correct answer)
• B. ['blue plate', 'glass plate', 'green plate', 'steel plate', 'white plate']
• C. ['green plate', 'steel plate', 'white plate']
• D. ['green plate', 'glass plate', 'blue plate']

Answer: A.Each push adds on top and each pop removes the top item: push blue plate gives ['blue plate']; push glass plate gives ['blue plate', 'glass plate']; push green plate gives ['blue plate', 'glass plate', 'green plate']; push steel plate gives ['blue plate', 'glass plate', 'green plate', 'steel plate']; push white plate gives ['blue plate', 'glass plate', 'green plate', 'steel plate', 'white plate']; pop removes white plate and leaves ['blue plate', 'glass plate', 'green plate', 'steel plate']; pop removes steel plate and leaves ['blue plate', 'glass plate', 'green plate'].

Q2. After push steel plate, push red plate, push white plate, push green plate, pop, pop, pop on an empty stack, which value is returned by the LAST pop?

• A. white plate
• B. steel plate
• C. red plate(correct answer)
• D. green plate

Answer: C.The last pop removes the item that was on top at that moment: push steel plate gives ['steel plate']; push red plate gives ['steel plate', 'red plate']; push white plate gives ['steel plate', 'red plate', 'white plate']; push green plate gives ['steel plate', 'red plate', 'white plate', 'green plate']; pop removes green plate and leaves ['steel plate', 'red plate', 'white plate']; pop removes white plate and leaves ['steel plate', 'red plate']; pop removes red plate and leaves ['steel plate'].

Q3. push white plate, push glass plate, push red plate, push green plate, push blue plate, pop, push steel plate, pop, pop: these operations run on an empty stack and each popped value is printed. In what order are the values printed?

• A. ['blue plate', 'steel plate', 'red plate']
• B. ['white plate', 'glass plate', 'red plate']
• C. ['blue plate', 'steel plate', 'green plate'](correct answer)
• D. ['green plate', 'steel plate', 'blue plate']

Answer: C.Every pop returns the current top item: push white plate gives ['white plate']; push glass plate gives ['white plate', 'glass plate']; push red plate gives ['white plate', 'glass plate', 'red plate']; push green plate gives ['white plate', 'glass plate', 'red plate', 'green plate']; push blue plate gives ['white plate', 'glass plate', 'red plate', 'green plate', 'blue plate']; pop removes blue plate and leaves ['white plate', 'glass plate', 'red plate', 'green plate']; push steel plate gives ['white plate', 'glass plate', 'red plate', 'green plate', 'steel plate']; pop removes steel plate and leaves ['white plate', 'glass plate', 'red plate', 'green plate']; pop removes green plate and leaves ['white plate', 'glass plate', 'red plate'].

Q4. push Book E, push Book B, push Book A, pop, push Book D, pop, push Book C, push Book F: these operations are applied in order to an empty stack. Which list shows the stack from bottom to top at the end?

• A. ['Book F', 'Book C', 'Book B', 'Book E']
• B. ['Book E', 'Book B', 'Book C', 'Book F'](correct answer)
• C. ['Book A', 'Book D', 'Book C', 'Book F']
• D. ['Book E', 'Book B', 'Book A', 'Book D', 'Book C', 'Book F']

Answer: B.Each push adds on top and each pop removes the top item: push Book E gives ['Book E']; push Book B gives ['Book E', 'Book B']; push Book A gives ['Book E', 'Book B', 'Book A']; pop removes Book A and leaves ['Book E', 'Book B']; push Book D gives ['Book E', 'Book B', 'Book D']; pop removes Book D and leaves ['Book E', 'Book B']; push Book C gives ['Book E', 'Book B', 'Book C']; push Book F gives ['Book E', 'Book B', 'Book C', 'Book F'].

Q5. push blue plate, push white plate, pop, push steel plate, push green plate, push red plate, push glass plate, pop: these operations are applied in order to an empty stack. Which list shows the stack from bottom to top at the end?

• A. ['steel plate', 'green plate', 'red plate', 'glass plate']
• B. ['blue plate', 'steel plate', 'green plate', 'red plate'](correct answer)
• C. ['red plate', 'green plate', 'steel plate', 'blue plate']
• D. ['blue plate', 'white plate', 'steel plate', 'green plate', 'red plate', 'glass plate']

Answer: B.Each push adds on top and each pop removes the top item: push blue plate gives ['blue plate']; push white plate gives ['blue plate', 'white plate']; pop removes white plate and leaves ['blue plate']; push steel plate gives ['blue plate', 'steel plate']; push green plate gives ['blue plate', 'steel plate', 'green plate']; push red plate gives ['blue plate', 'steel plate', 'green plate', 'red plate']; push glass plate gives ['blue plate', 'steel plate', 'green plate', 'red plate', 'glass plate']; pop removes glass plate and leaves ['blue plate', 'steel plate', 'green plate', 'red plate'].

Q6. After enqueue Zainab, enqueue Fatima, enqueue Ahmed, dequeue, enqueue Omar, dequeue, enqueue Ali, enqueue Noor on an empty queue, which value is returned by the LAST dequeue?

• A. Zainab
• B. Ahmed
• C. Fatima(correct answer)
• D. Noor

Answer: C.The last dequeue removes the front item at that moment: enqueue Zainab gives ['Zainab']; enqueue Fatima gives ['Zainab', 'Fatima']; enqueue Ahmed gives ['Zainab', 'Fatima', 'Ahmed']; dequeue removes Zainab and leaves ['Fatima', 'Ahmed']; enqueue Omar gives ['Fatima', 'Ahmed', 'Omar']; dequeue removes Fatima and leaves ['Ahmed', 'Omar']; enqueue Ali gives ['Ahmed', 'Omar', 'Ali']; enqueue Noor gives ['Ahmed', 'Omar', 'Ali', 'Noor'].

Q7. enqueue Job 4, enqueue Job 7, enqueue Job 1, dequeue, enqueue Job 6, enqueue Job 5, dequeue, dequeue: these operations run on an empty queue and each dequeued value is printed. In what order are the values printed?

• A. ['Job 7', 'Job 1', 'Job 4']
• B. ['Job 1', 'Job 5', 'Job 6']
• C. ['Job 1', 'Job 7', 'Job 4']
• D. ['Job 4', 'Job 7', 'Job 1'](correct answer)

Answer: D.Every dequeue returns the current front item: enqueue Job 4 gives ['Job 4']; enqueue Job 7 gives ['Job 4', 'Job 7']; enqueue Job 1 gives ['Job 4', 'Job 7', 'Job 1']; dequeue removes Job 4 and leaves ['Job 7', 'Job 1']; enqueue Job 6 gives ['Job 7', 'Job 1', 'Job 6']; enqueue Job 5 gives ['Job 7', 'Job 1', 'Job 6', 'Job 5']; dequeue removes Job 7 and leaves ['Job 1', 'Job 6', 'Job 5']; dequeue removes Job 1 and leaves ['Job 6', 'Job 5'].

Q8. After enqueue T103, enqueue T107, enqueue T106, dequeue, enqueue T102, enqueue T104, enqueue T101, dequeue on an empty queue, which value is returned by the LAST dequeue?

• A. T103
• B. T106
• C. T107(correct answer)
• D. T101

Answer: C.The last dequeue removes the front item at that moment: enqueue T103 gives ['T103']; enqueue T107 gives ['T103', 'T107']; enqueue T106 gives ['T103', 'T107', 'T106']; dequeue removes T103 and leaves ['T107', 'T106']; enqueue T102 gives ['T107', 'T106', 'T102']; enqueue T104 gives ['T107', 'T106', 'T102', 'T104']; enqueue T101 gives ['T107', 'T106', 'T102', 'T104', 'T101']; dequeue removes T107 and leaves ['T106', 'T102', 'T104', 'T101'].

Q9. enqueue Zainab, enqueue Fatima, enqueue Usman, dequeue, enqueue Ali, enqueue Bilal, dequeue, dequeue: these operations are applied in order to an empty queue. Which list shows the queue from front to back at the end?

• A. ['Zainab', 'Fatima']
• B. ['Ali', 'Bilal'](correct answer)
• C. ['Bilal', 'Ali']
• D. ['Zainab', 'Fatima', 'Usman', 'Ali', 'Bilal']

Answer: B.Items join at the back and leave from the front: enqueue Zainab gives ['Zainab']; enqueue Fatima gives ['Zainab', 'Fatima']; enqueue Usman gives ['Zainab', 'Fatima', 'Usman']; dequeue removes Zainab and leaves ['Fatima', 'Usman']; enqueue Ali gives ['Fatima', 'Usman', 'Ali']; enqueue Bilal gives ['Fatima', 'Usman', 'Ali', 'Bilal']; dequeue removes Fatima and leaves ['Usman', 'Ali', 'Bilal']; dequeue removes Usman and leaves ['Ali', 'Bilal'].

Q10. enqueue Job 3, enqueue Job 2, enqueue Job 4, dequeue, enqueue Job 7, dequeue, enqueue Job 1, dequeue: these operations are applied in order to an empty queue. Which list shows the queue from front to back at the end?

• A. ['Job 3', 'Job 2', 'Job 4', 'Job 7', 'Job 1']
• B. ['Job 7', 'Job 1'](correct answer)
• C. ['Job 3', 'Job 2']
• D. ['Job 1', 'Job 7']

Answer: B.Items join at the back and leave from the front: enqueue Job 3 gives ['Job 3']; enqueue Job 2 gives ['Job 3', 'Job 2']; enqueue Job 4 gives ['Job 3', 'Job 2', 'Job 4']; dequeue removes Job 3 and leaves ['Job 2', 'Job 4']; enqueue Job 7 gives ['Job 2', 'Job 4', 'Job 7']; dequeue removes Job 2 and leaves ['Job 4', 'Job 7']; enqueue Job 1 gives ['Job 4', 'Job 7', 'Job 1']; dequeue removes Job 4 and leaves ['Job 7', 'Job 1'].