Data Structure Questions and Answers – Stack using Linked List

This set of Data Structure Multiple Choice Questions & Answers (MCQs) focuses on “Stack using Linked List”.

1. What is the best case time complexity of deleting a node in a Singly Linked list?
a) O (n)
b) O (n²)
c) O (nlogn)
d) O (1)
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2. Which of the following statements are not correct with respect to Singly Linked List(SLL) and Doubly Linked List(DLL)?
a) Complexity of Insertion and Deletion at known position is O(n) in SLL and O(1) in DLL
b) SLL uses lesser memory per node than DLL
c) DLL has more searching power than SLL
d) Number of node fields in SLL is more than DLL
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3. 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 pop() operation that can be included in the Stack class. Also ‘first’ is the top-of-the-stack.

class Node
{
	protected Node next;
	protected Object ele;
	Node()
	{
		this(null,null);
	}
	Node(Object e,Node n)
	{
		ele=e;
		next=n;
	}
	public void setNext(Node n)
	{
		next=n;
	}
	public void setEle(Object e)
	{
		ele=e;
	}
	public Node getNext()
	{
		return next;
	}
	public Object getEle()
	{
		return ele;
	}
}
 
class Stack
{
	Node first;
	int size=0;
	Stack()
	{
		first=null;
	}
}

a)

public Object pop() 
{
	if(size == 0)
	System.out.println("underflow");
	else
	{
		Object o = first.getEle();
		first = first.getNext();
		size--;
		return o;
	}
}

b)

public Object pop() 
{
	if(size == 0)
	System.out.println("underflow");
	else
	{
		Object o = first.getEle();
		first = first.getNext().getNext();
		size--;
		return o;
	}
}

c)

public Object pop() 
{
	if(size == 0)
	System.out.println("underflow");
	else
	{
		first = first.getNext();
		Object o = first.getEle();
		size--;
		return o;
	}
}

d)

public Object pop() 
{
	if(size == 0)
	System.out.println("underflow");
	else
	{
		first = first.getNext().getNext();
		Object o = first.getEle();
		size--;
		return o;
	}
}

4. What does the following function do?

public Object some_func()throws emptyStackException
{
	if(isEmpty())
		throw new emptyStackException("underflow");
	return first.getEle();
}

a) pop
b) delete the top-of-the-stack element
c) retrieve the top-of-the-stack element
d) push operation
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5. What is the functionality of the following piece of code?

public void display() 
{
	if(size == 0)
		System.out.println("underflow");
	else
	{
		Node current = first;
		while(current != null)
		{
			System.out.println(current.getEle());
			current = current.getNext();
		}
	}
}

a) reverse the list
b) display the list
c) display the list excluding top-of-the-stack-element
d) reverse the list excluding top-of-the-stack-element
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6. What does ‘stack overflow’ refer to?
a) accessing item from an undefined stack
b) adding items to a full stack
c) removing items from an empty stack
d) index out of bounds exception
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7. 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 ‘first’ is the top-of-the-stack.

class Node
{
	protected Node next;
	protected Object ele;
	Node()
	{
		this(null,null);
	}
	Node(Object e,Node n)
	{
		ele=e;
		next=n;
	}
	public void setNext(Node n)
	{
		next=n;
	}
	public void setEle(Object e)
	{
		ele=e;
	}
	public Node getNext()
	{
		return next;
	}
	public Object getEle()
	{
		return ele;
	}
}
 
class Stack
{
	Node first;
	int size=0;
	Stack()
	{
		first=null;
	}
}

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++;
}

8. 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();
push(5);
top();

a) 20
b) 4
c) stack underflow
d) 5
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9. Which of the following data structures can be used for parentheses matching?
a) n-ary tree
b) queue
c) priority queue
d) stack
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10. Minimum number of queues to implement stack is ___________
a) 3
b) 4
c) 1
d) 2
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