Stacks & Queues

What method is used to return the top of the stack?

• remove (element)

• pop()

• pop (position)

• peek()

A stack is implemented in Python using the built-in list data structure. What Python method is used to implement push() function?

• insert()

• append()

• add()

• delete()

A stack is implemented in Python using the built-in list data structure. Complete this code of function size() within the Stack class.

class Stack:

def __init__(self):

self.items = [ ]

def size(self):

…………………

• return len(self.items)

• stack.length

• return len(stack)

• return length(self.items)

A stack is implemented in Python using the built-in list data structure. Complete this code of function peek() within the Stack class.

class Stack:

def __init__(self):

self.items = [ ]

def peek(self):

…………………

• return self.items[len(self.items)]

• return self.items[stack.length]

• return self.items[stack.length-1]

• return self.items[len(self.items)-1]

The following operations are performed on a Stack.

s=Stack()

s.push(‘a’)

s.push(‘b’)

s.pop()

s.push(‘c’)

s.peek()

What is the top of the Stack s when these operations are complete?

• 'a'

• 'b'

• 'c'

• Stack is empty

The following operations are performed on a Stack.

s=Stack()

s.push(‘a’)

s.push(‘b’)

s.push(‘c’)

while not s.isEmpty():

s.pop()

s.pop()

What is the top of the Stack s when these operations are complete?

• 'a'

• 'b'

• Empty stack

• Error

stack colours=(‘Red’, ‘Green’, ‘Blue’)

What is the value of top of the stack colours?

• -1

• 'Red'

• 'Green'

• 'Blue'

stack colours=(‘Red’, ‘Green’, ‘Blue’)

What is the value of the top of the stack colours after pop() operation is performed twice?

• Empty stack

• 'Red'

• 'Green'

• 'Blue'

stack colours=(‘Red’, ‘Green’, ‘Blue’)

colours.push(‘Black’) is executed. Stack colours=………………..?

• ('Black', 'Red', 'Green', 'Blue')

• ('Black', 'Blue')

• (''Red', 'Green', 'Blue', 'Black')

• Error

Which of the following is NOT a part of stack frame?

• Local variable

• Return address

• Global variables

• Parameters