Explore topic-wise MCQs in Data Structures and Algorithms.

This section includes 66 Mcqs, each offering curated multiple-choice questions to sharpen your Data Structures and Algorithms knowledge and support exam preparation. Choose a topic below to get started.

1.

Which of the following is an example for a postfix expression?

A. a*b(c+d)
B. abc*+de
C. +ab
D. a+b-c
Answer» C. +ab
Discussion
2.

An error is thrown if the character '\n' is pushed in to the character stack.

A. true
B. false
Answer» C.
Discussion
3.

How many passes does the balancing symbols algorithm makes through the input?

A. one
B. two
C. three
D. four
Answer» B. two
Discussion
4.

The postfix expression abc+de/*- is equivalent to which of the following infix expression

A. abc+-de*/
B. (a+b)-d/e*c
C. a-(a+b)*(d/e)
D. abc+*-(d/e)
Answer» D. abc+*-(d/e)
Discussion
5.

When the corresponding end bracket/braces/parentheses is not found, what happens?

A. The stack is popped
B. Ignore the parentheses
C. An error is reported
D. It is treated as an exception
Answer» D. It is treated as an exception
Discussion
6.

What is the value of the postfix expression 2 3 + 4 5 6 – – *

A. 19
B. 21
C. 23
D. -2
Answer» C. 23
Discussion
7.

If -*+abcd = 11, find a, b, c, d using evaluation of prefix algorithm.

A. a=2, b=3, c=5, d=4
B. a=1, b=2, c=5, d=4
C. a=5, b=4, c=7,d=5
D. a=1, b=2, c=3, d=4
Answer» C. a=5, b=4, c=7,d=5
Discussion
8.

In Postfix expressions, the operators come after the operands.

A. True
B. False
Answer» B. False
Discussion
9.

What should be done when a left parenthesis '(' is encountered?

A. It is ignored
B. It is placed in the output
C. It is placed in the operator stack
D. The contents of the operator stack is emptied
Answer» D. The contents of the operator stack is emptied
Discussion
10.

What determines the order of evaluation of a prefix expression?

A. precedence and associativity
B. precedence only
C. associativity only
D. depends on the parser
Answer» B. precedence only
Discussion
11.

Using the evaluation of prefix algorithm, evaluate +-9 2 7.

A. 10
B. 4
C. 17
D. 14
Answer» E.
Discussion
12.

Reverse Polish Notation is the reverse of a Polish Notation

A. True
B. False
Answer» C.
Discussion
13.

When converting the prefix notation into an infix notation, the first step to be followed is ________

A. Reverse the equation
B. Push the equation to the stack
C. Push the equation onto the queue
D. Push the equation to the stack or queue
Answer» B. Push the equation to the stack
Discussion
14.

How many stacks are required for evaluation of prefix expression?

A. one
B. two
C. three
D. four
Answer» C. three
Discussion
15.

How many types of input characters are accepted by this algorithm?

A. one
B. two
C. three
D. four
Answer» D. four
Discussion
16.

What is the time complexity of balancing parentheses algorithm?

A. O (N)
B. O (N log N)
C. O (M log N)
D. O (N2)
Answer» B. O (N log N)
Discussion
17.

Which of the following is not an application of stack?

A. evaluation of postfix expression
B. conversion of infix to postfix expression
C. balancing symbols
D. line at ticket counter
Answer» E.
Discussion
18.

What will be the word obtained if the word 'abbcabb' is reversed using a stack?

A. bbabbca
B. abbcabb
C. bbacbba
D. bbacabb
Answer» D. bbacabb
Discussion
19.

The result of the postfix expression 5 3 * 9 + 6 / 8 4 / + is

A. 8
B. 6
C. 10
D. 9
Answer» C. 10
Discussion
20.

If the corresponding end bracket/braces/parentheses is encountered, which of the following is done?

A. push it on to the stack
B. pop the stack
C. throw an error
D. treated as an exception
Answer» C. throw an error
Discussion
21.

The equivalent infix expression and value for the postfix form 1 2 + 3 * 4 5 * – will be

A. 1 + 2 * 3 – 4 * 5 and -13
B. (2 + 1) * (3 – 4) * 5 and 13
C. 1 + 2 * (3 – 4) * 5 and -11
D. (1 + 2) * 3 – (4 * 5) and -11
Answer» E.
Discussion
22.

Given two processes (conversion of postfix equation to infix notation and conversion of prefix notation to infix notation), which of the following is easier to implement?

A. Both are easy to implement
B. Conversion of postfix equation to infix equation is harder than converting a prefix notation to infix notation
C. Conversion of postfix equation to infix equation is easier than converting a prefix notation to infix notation
D. Insufficient data
Answer» D. Insufficient data
Discussion
23.

What data structure is used when converting an infix notation to prefix notation?

A. Stack
B. Queue
C. B-Trees
D. Linked-list
Answer» B. Queue
Discussion
24.

The prefix expression of the postfix expression AB+CD-* is

A. (A+B)*(C-D)
B. +AB*-CD
C. A+*BCD-
D. *+AB-CD
Answer» E.
Discussion
25.

Which application of stack is used to ensure that the pair of parentheses is properly nested?

A. Balancing symbols
B. Reversing a stack
C. Conversion of an infix to postfix expression
D. Conversion of an infix to prefix expression
Answer» B. Reversing a stack
Discussion
26.

The associativity of an exponentiation operator ^ is right side.

A. True
B. False
Answer» B. False
Discussion
27.

Which of the following does the balancing symbols algorithm include?

A. balancing double quotes
B. balancing single quotes
C. balancing operators and brackets
D. balancing parentheses, brackets and braces
Answer» E.
Discussion
28.

In balancing parentheses algorithm, the string is read from?

A. right to left
B. left to right
C. center to right
D. center to left
Answer» C. center to right
Discussion
29.

Evaluate the postfix expression ab + cd/- where a=5, b=4, c=9, d=3.

A. 23
B. 15
C. 6
D. 10
Answer» D. 10
Discussion
30.

In infix to postfix conversion algorithm, the operators are associated from?

A. right to left
B. left to right
C. centre to left
D. centre to right
Answer» C. centre to left
Discussion
31.

Which of the following statement is invalid with respect to balancing symbols?

A. [(A+B) + (C-D)]
B. [{A+B}-{C-[D+E]}]
C. ((A+B) + (C+D)
D. {(A+B) + [C+D]}
Answer» D. {(A+B) + [C+D]}
Discussion
32.

It is easier for a computer to process a postfix expression than an infix expression.

A. True
B. False
Answer» B. False
Discussion
33.

While evaluating a postfix expression, when an operator is encountered, what is the correct operation to be performed?

A. push it directly on to the stack
B. pop 2 operands, evaluate them and push the result on to the stack
C. pop the entire stack
D. ignore the operator
Answer» C. pop the entire stack
Discussion
34.

Which is the most appropriate data structure for applying balancing of symbols algorithm?

A. stack
B. queue
C. tree
D. graph
Answer» B. queue
Discussion
35.

Is the given statement ((A+B) + [C-D]] valid with respect to balancing of symbols?

A. True
B. False
Answer» C.
Discussion
36.

What should be done when an opening parentheses is read in a balancing symbols algorithm?

A. push it on to the stack
B. throw an error
C. ignore the parentheses
D. pop the stack
Answer» B. throw an error
Discussion
37.

Which of the following statement is incorrect with respect to infix to postfix conversion algorithm?

A. operand is always placed in the output
B. operator is placed in the stack when the stack operator has lower precedence
C. parenthesis are included in the output
D. higher and equal priority operators follow the same condition
Answer» D. higher and equal priority operators follow the same condition
Discussion
38.

What will be output if the following sequence of operations are executed?Push(a,s);Push(b,s);Pop(b);Push(c,s);

A. abc
B. b
C. ac
D. acb
Answer» C. ac
Discussion
39.

Consider the postfix expression 4 5 6 a b 7 8 a c, where a, b, c are operators. Operator a has higher precedence over operators b and c. Operators b and c are right associative. Then, equivalent infix expression is

A. 4 a 5 6 b 7 8 a c
B. 4 a 5 c 6 b 7 a 8
C. 4 b 5 a 6 c 7 a 8
D. 4 a 5 b 6 c 7 a 8
Answer» D. 4 a 5 b 6 c 7 a 8
Discussion
40.

The time complexity of converting a prefix notation to infix notation is _________

A. O(n) where n is the length of the equation
B. O(n) where n is number of operands
C. O(1)
D. O(logn) where n is length of the equation
Answer» B. O(n) where n is number of operands
Discussion
41.

Which of the following is an infix expression?

A. (a+
B. *(c+d)b) ab+c*
C. +ab
D. abc+*
Answer» B. *(c+d)b) ab+c*
Discussion
42.

What is the time complexity of the above code?

A. O(logn)
B. O(n)
C. O(1)
D. O(nlogn)
Answer» C. O(1)
Discussion
43.

Find the output of the following prefix expression*+2-2 1/-4 2+-5 3 1

A. 2
B. 12
C. 10
D. 4
Answer» B. 12
Discussion
44.

What is the number of moves required in the Tower of Hanoi problem for k disks?

A. 2k – 1
B. 2k + 1
C. 2k + 1
D. 2k – 1
Answer» E.
Discussion
45.

What is the time complexity of evaluation of postfix expression algorithm?

A. O (N)
B. O (N log N)
C. O (N2)
D. O (M log N)
Answer» B. O (N log N)
Discussion
46.

An error is reported when the stack is not empty at the end.

A. True
B. False
Answer» B. False
Discussion
47.

Evaluate and write the result for the following postfix expression abc*+de*f+g*+ where a=1, b=2, c=3, d=4, e=5, f=6, g=2.

A. 61
B. 59
C. 60
D. 55
Answer» C. 60
Discussion
48.

Express -15 as a 6-bit signed binary number.

A. 1111
B. 101111
C. 101110
D. 1110
Answer» C. 101110
Discussion
49.

Consider the stack| 5 || 4 || 3 || 2 |.At this point, '*' is encountered. What has to be done?

A. 5*4=20 is pushed into the stack
B. * is pushed into the stack
C. 2*3=6 is pushed into the stack
D. * is ignored
Answer» B. * is pushed into the stack
Discussion
50.

Which of the following data structure is used to convert postfix expression to infix expression?

A. Stack
B. Queue
C. Linked List
D. Heap
Answer» B. Queue
Discussion