Push Operation on Stack in DSA C# - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to push an element onto the stack.

DSA C#

stack.[1](value);

Drag options to blanks, or click blank then click option'

APeek

BPop

CPush

DClear

Attempts:

3 left

💡 Hint

Common Mistakes

Using Pop instead of Push removes an element instead of adding.

Using Peek only looks at the top element without adding.

Clear empties the stack instead of adding.

The Push method adds an element to the top of the stack.

2fill in blank

medium

Complete the code to create a new stack of integers.

DSA C#

Stack<int> stack = new Stack<[1]>();

Drag options to blanks, or click blank then click option'

Adouble

Bstring

Cbool

Dint

Attempts:

3 left

💡 Hint

Common Mistakes

Using string or bool types when integers are needed.

Using double which is for decimal numbers.

The stack is created to hold integers, so the type is int.

3fill in blank

hard

Fix the error in the push operation code.

DSA C#

stack.[1](item);

Drag options to blanks, or click blank then click option'

APush

BpopItem

CPeek

DPop

Attempts:

3 left

💡 Hint

Common Mistakes

Using Pop removes an element instead of adding.

Using Peek only views the top element.

popItem is not a valid method.

The correct method to add an item is Push. Other options either remove or look at items.

4fill in blank

hard

Fill both blanks to push the number 10 onto the stack and then print the top element.

DSA C#

stack.[1](10);
Console.WriteLine(stack.[2]());

Drag options to blanks, or click blank then click option'

APush

BPop

CPeek

DClear

Attempts:

3 left

💡 Hint

Common Mistakes

Using Pop removes the element instead of viewing.

Using Clear empties the stack.

Push adds 10 to the stack. Peek shows the top element without removing it.

5fill in blank

hard

Fill all three blanks to push three numbers onto the stack and then print the top element.

DSA C#

stack.[1](5);
stack.[2](15);
stack.[3](25);
Console.WriteLine(stack.Peek());

Drag options to blanks, or click blank then click option'

APush

BPop

CPeek

DClear

Attempts:

3 left

💡 Hint

Common Mistakes

Using Pop or Peek to add elements is incorrect.

Using Clear empties the stack.

Use Push to add each number to the stack. Peek then shows the top element.

Practice

1. What does the Push operation do in a stack?

easy

A. Adds an element to the top of the stack

B. Removes the top element from the stack

C. Returns the bottom element of the stack

D. Checks if the stack is empty

Solution

1. Step 1: Understand stack behavior

   A stack follows Last In First Out (LIFO) principle, where elements are added or removed from the top.

2. Step 2: Define Push operation

   The Push operation adds a new element on top of the stack, increasing its size by one.

3. Final Answer:

   Adds an element to the top of the stack -> Option A

4. Quick Check:

   Push = Add top element [OK]

Hint: Push means add on top of stack [OK]

Common Mistakes:

• Confusing Push with Pop operation
• Thinking Push removes elements
• Assuming Push accesses bottom element

2. Which of the following is the correct syntax to push an integer value 10 onto a stack named stack in C#?

easy

A. stack.Insert(10);

B. stack.Add(10);

C. stack.Push(10);

D. stack.Push = 10;

Solution

1. Step 1: Recall Stack method for adding elements

   In C#, the Stack class uses the method Push() to add elements.

2. Step 2: Check syntax correctness

   The correct syntax is calling Push with the value inside parentheses: stack.Push(10);

3. Final Answer:

   stack.Push(10); -> Option C

4. Quick Check:

   Push method call syntax = stack.Push(value) [OK]

Hint: Use stack.Push(value) to add elements [OK]

Common Mistakes:

• Using Add or Insert which are not stack methods
• Assigning value directly to Push
• Missing parentheses in method call

3. What will be the output after executing the following C# code?

Stack<int> stack = new Stack<int>();
stack.Push(5);
stack.Push(10);
stack.Push(15);
Console.WriteLine(string.Join(", ", stack));

medium

A. 5, 10, 15

B. 15, 10, 5

C. 10, 15, 5

D. 15, 5, 10

Solution

1. Step 1: Understand push order and stack iteration

   Elements pushed are 5, then 10, then 15. Stack stores last pushed on top.

2. Step 2: Determine iteration order when printing

   Stack enumerates from top to bottom, so output order is 15, 10, 5.

3. Final Answer:

   15, 10, 5 -> Option B

4. Quick Check:

   Stack top to bottom = 15, 10, 5 [OK]

Hint: Stack prints top element first [OK]

Common Mistakes:

• Assuming stack prints in push order
• Confusing stack with queue order
• Forgetting stack is LIFO

4. Identify the error in the following C# code that tries to push elements onto a stack:

Stack<string> stack = new Stack<string>();
stack.Push "hello";
stack.Push("world");

medium

A. Push method does not exist

B. Stack cannot hold strings

C. Missing semicolon after second Push

D. Missing parentheses in first Push call

Solution

1. Step 1: Check syntax of Push calls

   The first Push call is written as stack.Push "hello"; missing parentheses.

2. Step 2: Confirm correct method usage

   Push requires parentheses around argument: stack.Push("hello");

3. Final Answer:

   Missing parentheses in first Push call -> Option D

4. Quick Check:

   Method calls need parentheses [OK]

Hint: Always use parentheses with method calls [OK]

Common Mistakes:

• Ignoring parentheses syntax
• Thinking stack can't hold strings
• Assuming missing semicolon causes error here

5. Given a stack initially empty, what will be the content of the stack after executing the following code?

Stack<int> stack = new Stack<int>();
for (int i = 1; i <= 3; i++)
{
    stack.Push(i * 2);
}
stack.Push(10);
stack.Push(stack.Pop() + 5);

hard

A. 15, 6, 4, 2

B. 10, 8, 4, 2

C. 15, 10, 6, 4, 2

D. 10, 15, 6, 4, 2

Solution

1. Step 1: Trace the for loop pushing values

   Loop pushes 2, 4, 6 in order. Stack top is 6, bottom is 2.

2. Step 2: Push 10, then pop top and push pop+5

   Push 10: stack top to bottom 10, 6, 4, 2. Pop removes 10, 10 + 5 = 15, push 15: top to bottom 15, 6, 4, 2.

3. Final Answer:

   15, 6, 4, 2 -> Option A

4. Quick Check:

   Stack after operations = 15, 6, 4, 2 [OK]

Hint: Track push/pop stepwise to find final stack [OK]

Common Mistakes:

• Confusing pop value used for new push
• Forgetting pop removes top element
• Assuming push adds without removing