# Balanced Parenthesis Multiple Choice Questions and Answers (MCQs)

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This set of Data Structures & Algorithms Multiple Choice Questions & Answers (MCQs) focuses on “Balanced Parenthesis”.

1. 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)

Explanation: The time complexity of balancing parentheses algorithm is mathematically found to be O (N).

2. 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

Explanation: Balancing symbols application ensures that the pair of parentheses are properly nested while reversing stack reverses a stack.

3. 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

Explanation: Any string is read by the compiler from left to right and not from right to left.

4. Which is the most appropriate data structure for applying balancing of symbols algorithm?
a) stack
b) queue
c) tree
d) graph

Explanation: Stack is the most appropriate data structure for balancing symbols algorithm because stack follows LIFO principle (Last In First Out).

5. 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

Explanation: The balancing symbols algorithm using stack only includes balancing parentheses, brackets and braces and not any other symbols.
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6. Which of the following statement is incorrect with respect to balancing symbols algorithm?
a) {[()]}
b) ([ )]
c) {( )}
d) { [ ] }

Explanation: ([ )] is incorrect because’)’ occurs before the corresponding ‘]’ is encountered.

7. 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

Explanation: When an opening bracket/braces/parentheses is encountered, it is pushed on to the stack. When the corresponding end bracket/braces/parentheses is not found, throw an error.

a) The stack is popped
b) Ignore the parentheses
c) An error is reported
d) It is treated as an exception

Explanation: When the corresponding end bracket/braces/parentheses is not found, throw an error since they don’t match.

9. 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

Explanation: When the corresponding end bracket/braces/parentheses is encountered, the stack is popped. When an opening bracket/braces/parentheses is encountered, it is pushed on to the stack.

10. An error is reported when the stack is not empty at the end.
a) True
b) False

Explanation: When the stack contains elements at the end, it means that the given string of parentheses is not balanced.

11. Is the given statement ((A+B) + [C-D]] valid with respect to balancing of symbols?
a) True
b) False

Explanation: The given statement is invalid with respect to balancing of symbols because the last parentheses do not correspond to the opening braces.

12. How many passes does the balancing symbols algorithm makes through the input?
a) one
b) two
c) three
d) four

Explanation: The balancing symbols algorithm makes only one pass through the input since it is linear.

13. 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]}

Explanation: ((A+B) + (C+D) is invalid because the last close parentheses is not found in the statement.

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