Push Operation on Stack in DSA Typescript - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to add an element to the top of the stack.

DSA Typescript

stack.[1](5);

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

Ashift

Bpop

Cpeek

Dpush

Attempts:

3 left

💡 Hint

Common Mistakes

Using pop instead of push removes an element instead of adding.

Using peek only views the top element without adding.

Using shift removes the first element, not related to stack push.

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

2fill in blank

medium

Complete the code to push a variable value onto the stack.

DSA Typescript

const value = 10;
stack.[1](value);

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

Apop

Bpush

Cunshift

Dslice

Attempts:

3 left

💡 Hint

Common Mistakes

Using pop removes elements instead of adding.

Using unshift adds to the front, not the top of the stack.

Use push to add the variable value to the stack.

3fill in blank

hard

Fix the error in the push operation code.

DSA Typescript

stack.[1] = 20;

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

Alength

Bpop

Cpush

Dtop

Attempts:

3 left

💡 Hint

Common Mistakes

Trying to assign a value to push instead of calling push as a function.

Using pop or length incorrectly to add elements.

You cannot assign a value directly to push. Instead, call push as a method with parentheses.

4fill in blank

hard

Fill both blanks to push the sum of two numbers onto the stack.

DSA Typescript

const a = 3;
const b = 7;
stack.[1](a [2] b);

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

Apush

B+

C-

Dpop

Attempts:

3 left

💡 Hint

Common Mistakes

Using pop instead of push removes elements.

Using minus (-) subtracts instead of adding.

Use push to add the sum a + b to the stack.

5fill in blank

hard

Fill all three blanks to push the uppercase version of a string onto the stack.

DSA Typescript

const word = 'hello';
stack.[1](word.[2]().[3]());

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

Apush

BtoUpperCase

Ctrim

Dpop

Attempts:

3 left

💡 Hint

Common Mistakes

Using pop instead of push.

Mixing order of trim and toUpperCase methods.

First trim spaces with trim(), then convert to uppercase with toUpperCase(), and push the result onto the stack.

Practice

1. What does the push operation do in a stack data structure?

easy

A. Returns the bottom element of the stack

B. Removes the top element from the stack

C. Adds an element to the top 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 existing elements in the stack.

3. Final Answer:

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

4. Quick Check:

   Push = Add top [OK]

Hint: Push always adds on top of stack [OK]

Common Mistakes:

• Confusing push with pop operation
• Thinking push removes elements
• Mixing stack with queue operations

2. Which of the following is the correct TypeScript syntax to push an element 5 into a stack array named stack?

easy

A. stack.push(5);

B. stack.add(5);

C. push(stack, 5);

D. stack.insert(5);

Solution

1. Step 1: Recall TypeScript array push method

   In TypeScript, arrays have a built-in method push() to add elements at the end (top for stack).

2. Step 2: Match syntax

   The correct syntax is calling push on the array with the element as argument: stack.push(5);

3. Final Answer:

   stack.push(5); -> Option A

4. Quick Check:

   Array push method = stack.push(value) [OK]

Hint: Use array.push(element) to push [OK]

Common Mistakes:

• Using non-existent methods like add or insert
• Calling push as a standalone function
• Forgetting parentheses after push

3. What will be the content of the stack after executing the following TypeScript code?

const stack: number[] = [];
stack.push(10);
stack.push(20);
stack.push(30);

medium

A. [30, 20, 10]

B. [10, 20, 30]

C. [10, 30, 20]

D. [20, 10, 30]

Solution

1. Step 1: Trace each push operation

   Initially, stack is empty []. After push(10), stack = [10]. After push(20), stack = [10, 20]. After push(30), stack = [10, 20, 30].

2. Step 2: Understand stack order

   The first pushed element is at index 0, last pushed at the end. So the array shows bottom to top as left to right.

3. Final Answer:

   [10, 20, 30] -> Option B

4. Quick Check:

   Push order = [10, 20, 30] [OK]

Hint: Stack array shows bottom to top left to right [OK]

Common Mistakes:

• Reversing the order of elements
• Confusing push with pop output
• Assuming push adds at start of array

4. Identify the error in the following TypeScript code that tries to push an element into a stack:

let stack: number[] = [1, 2, 3];
stack.push 4;

medium

A. Missing parentheses after push

B. Stack should be declared as const

C. push cannot be used on arrays

D. Missing semicolon after array declaration

Solution

1. Step 1: Check push method syntax

   The push method requires parentheses to pass the element: stack.push(4);. The code uses stack.push 4; which is invalid.

2. Step 2: Verify other parts

   Declaring stack with let is valid. push is valid on arrays. Semicolon is optional but not an error here.

3. Final Answer:

   Missing parentheses after push -> Option A

4. Quick Check:

   push() needs parentheses [OK]

Hint: Always use parentheses with push method [OK]

Common Mistakes:

• Omitting parentheses on method calls
• Thinking push is a property, not a method
• Confusing let and const errors

5. Given a stack implemented as an array, how can you push multiple elements [4, 5, 6] onto the stack in one operation while preserving their order (4 at bottom, 6 at top)?

hard

A. Use stack.unshift(...[4, 5, 6])

B. Use stack.push([4, 5, 6])

C. Use a loop to push each element from left to right

D. Use stack.push(...[4, 5, 6])

Solution

1. Step 1: Understand spread operator with push

   Using stack.push(...[4, 5, 6]) spreads the array elements as separate arguments, pushing 4, then 5, then 6 in order.

2. Step 2: Compare other options

   stack.push([4, 5, 6]) pushes the entire array as one element, not separate elements.
   Looping works but is multiple operations, not one.
   unshift adds elements at the start, not top of stack.

3. Final Answer:

   Use stack.push(...[4, 5, 6]) -> Option D

4. Quick Check:

   Spread operator with push adds multiple elements [OK]

Hint: Use spread operator ... with push for multiple elements [OK]

Common Mistakes:

• Pushing array as single element instead of separate
• Using unshift which adds at bottom
• Forgetting spread operator syntax