Stack Reversal using Recursion Multiple Choice Questions and Answers (MCQs)

This set of Data Structures & Algorithms Multiple Choice Questions & Answers (MCQs) focuses on “Stack Reversal using Recursion”.

1. Which of the following statement is true about stack?
a) Pop operation removes the top most element
b) Pop operation removes the bottom most element
c) Push operation adds new element at the bottom
d) Push operation removes the top most element
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2. What is the space complexity of program to reverse stack recursively?
a) O(1)
b) O(log n)
c) O(n)
d) O(n log n)
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3. Stack can be reversed without using extra space by _____________
a) using recursion
b) using linked list to implement stack
c) using an extra stack
d) it is not possible
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4. Which of the following is considered as the top of the stack in the linked list implementation of the stack?
a) Last node
b) First node
c) Random node
d) Middle node
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5. What is the time complexity of the program to reverse stack when linked list is used for its implementation?
a) O(n)
b) O(n log n)
c) O(n²)
d) O(log n)
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6. Which of the following takes O(n) time in worst case in array implementation of stack?
a) pop
b) push
c) isEmpty
d) pop, push and isEmpty takes constant time
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7. What will be the time complexity of the code to reverse stack recursively?
a) O(n)
b) O(n log n)
c) O(log n)
d) O(n²)
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8. Which of the following functions correctly represents the recursive approach to reverse a stack?
a)

int reverse()
{
    if(s.size()<0)
    {
        int x = s.top();
        s.pop();
        reverse();
        BottomInsert(x);
    }
}

b)

int reverse()
{
    if(s.size()>=0)
    {
        int x = s.top();
        s.pop();
        reverse();
        BottomInsert(x);
    }
}

c)

int reverse()
{
    if(s.size()>0)
    {
        int x = s.top();
        s.pop();
        reverse();
        BottomInsert(x);
    }
}

d)

int reverse()
{
    if(s.size()>0)
    {
        int x = s.top();
        BottomInsert(x);
        s.pop();
        reverse();
    }
}

9. Which of the following correctly represents the function to insert elements at the bottom of stack?
a)

 int BottomInsert(int x)
 {
	if(s.size()!=0) s.push(x);
	else
	{
		int a = s.top();
		s.pop();
		BottomInsert(x);
		s.push(a);
	}
}

b)

int BottomInsert(int x)
{
	if(s.size()==0) s.push(x);
	else
	{
		int a = s.top();
		s.pop();
		s.push(a);
		BottomInsert(x);
	}
}

c)

int BottomInsert(int x)
{
	if(s.size()==0) s.push(x);
	else
	{
		int a = s.top();
		s.pop();
		BottomInsert(x);
		s.push(a);
	}
}

d)

int BottomInsert(int x)
{
	if(s.size()==0) s.push(x);
	else
	{
		s.pop();
		int a = s.top();
		BottomInsert(x);
		s.push(a);
	}
}

10. Which of the following code correctly represents the function to reverse stack without using recursion?
a)

 #include <stack>
void reverseStack(stack<int> &input, stack<int> &extra)
{
	while(input.size()!=0)
	{
		extra.push(input.top());
		input.pop();
    }
    input.swap(extra);
}

b)

 #include <stack>
void reverseStack(stack<int> &input, stack<int> &extra)
{
	while(input.size()!=0)
    {
		extra.push(input.top());
		input.pop();
    }
    extra.swap(input);
}

c)

 #include <stack>
void reverseStack(stack<int> &input, stack<int> &extra)
{
    while(input.size()!=0)
    {
		input.pop();
		extra.push(input.top());
    }
    extra.swap(input);
}

d)

#include <stack>
void reverseStack(stack<int> &input, stack<int> &extra)
{
   while(input.size()==0)
   {
		input.pop();
		extra.push(input.top());
   }
   extra.swap(input);
}

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