Stacks MCQs | Data Structure

MCQ

151.

Given below is the Node class to perform basic list operations and a Stack class with a no arg constructor. Select from the options the appropriate push() operation that can be included in the Stack class. Also

A

public void push(Object item)
{
	Node temp = new Node(item,first);
	first = temp;
	size++;
}

B

public void push(Object item)
{
	Node temp = new Node(item,first);
	first = temp.getNext();
	size++;
}

C

public void push(Object item)
{
	Node temp = new Node();
	first = temp.getNext();
	first.setItem(item);
	size++;
}

D

public void push(Object item)
{
	Node temp = new Node();
	first = temp.getNext.getNext();
	first.setItem(item);
	size++;
}

Discussion

MCQ

152.

Consider these functions:
push() : push an element into the stack

pop() : pop the top-of-the-stack element

top() : returns the item stored in top-of-the-stack-node

What will be the output after performing these sequence of operations

push(20);

push(4);

top();

pop();

pop();

pop();

push(5);

top();

A

20

B

4

C

stack underflow

D

5

Discussion

MCQ

153.

Which of the following data structures can be used for parentheses matching?

A

n-ary tree

B

queue

C

priority queue

D

stack

Discussion

MCQ

154.

Minimum number of queues to implement stack is ___________

A

3

B

4

C

1

D

2

Discussion

MCQ

155.

To implement a stack using queue(with only enqueue and dequeue operations), how many queues will you need?

A

1

B

2

C

3

D

4

Discussion

MCQ

156.

Making the push operation costly, select the code snippet which implements the same.(let q1 and q2 be two queues)

A

public void push(int x)
{
        if(empty())
        {
            q1.offer(x);
        }
        else{
                if(q1.size()>0)
                {
                    q2.offer(x);
                    int size = q1.size();
                    while(size>0)
                    {
                        q2.offer(q1.poll());
                        size--;
                    }
                }
            else if(q2.size()>0)
            {
                q1.offer(x);
                int size = q2.size();
                while(size>0)
                {
                    q1.offer(q2.poll());
                    size--;
                }
            }
        }
    }

B

public void push(int x)
{
        if(empty())
        {
            q1.offer(x);
        }
        else
        {
            if(q1.size()>0)
            {
                q1.offer(x);
                int size = q1.size();
                while(size>0)
                {
                    q2.offer(q1.poll());
                    size--;
                }
            }
            else if(q2.size()>0)
            {
                q2.offer(x);
                int size = q2.size();
                while(size>0)
                {
                    q1.offer(q2.poll());
                    size--;
                }
            }
        }
}

C

public void push(int x)
{
        if(empty())
        {
            q1.offer(x);
        }
        else
        {
            if(q1.size()>0)
            {
                q2.offer(x);
                int size = q1.size();
                while(size>0)
                {
                    q1.offer(q2.poll());
                    size--;
                }
            }
            else if(q2.size()>0)
            {
                q1.offer(x);
                int size = q2.size();
                while(size>0)
                {
                    q2.offer(q1.poll());
                    size--;
                }
            }
        }
}

D

public void push(int x)
{
        if(empty())
        {
            q1.offer(x);
        }
        else
        {
            if(q1.size()>0)
            {
                q2.offer(x);
                int size = q1.size();
                while(size>0)
                {
                    q2.offer(q2.poll());
                    size--;
                }
            }
            else if(q2.size()>0)
            {
                q1.offer(x);
                int size = q2.size();
                while(size>0)
                {
                    q2.offer(q1.poll());
                    size--;
                }
            }
        }
}

Discussion

MCQ

157.

Select the code snippet which returns the top of the stack.

A

public int top()
{
       if(q1.size()>0)
       {
            return q1.poll();
       }
       else if(q2.size()>0)
       {
            return q2.poll();
       }
       return 0;
}

B

public int top()
{
       if(q1.size()==0)
       {
            return q1.peek();
       }
       else if(q2.size()==0)
       {
            return q2.peek();
       }
        return 0;
    }

C

public int top()
{
       if(q1.size()>0)
       {
            return q1.peek();
       }
       else if(q2.size()>0)
       {
            return q2.peek();
       }
       return 0;
}

D

public int top()
{
       if(q1.size()>0)
       {
            return q2.peek();
       }
       else if(q2.size()>0)
       {
            return q1.peek();
       }
       return 0;
}

Discussion

MCQ

158.

Select the code snippet which return true if the stack is empty, false otherwise.

A

public boolean empty()
{
     return q2.isEmpty();
}

B

public boolean empty() 
{
     return q1.isEmpty() || q2.isEmpty();
}

C

public boolean empty() 
{
     return q1.isEmpty();
}

D

public boolean empty() 
{
     return q1.isEmpty() & q2.isEmpty();
}

Discussion

MCQ

159.

Which is the predefined method available in Java to convert decimal to binary numbers?

A

toBinaryInteger(int)

B

toBinaryValue(int)

C

toBinaryNumber(int)

D

toBinaryString(int)

Discussion

MCQ

160.

What is the time complexity for converting decimal to binary numbers?

A

O(1)

B

O(n)

C

O(logn)

D

O(nlogn)

Discussion

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