Enqueue Operation in DSA Typescript - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to add an element to the end of the queue.

DSA Typescript

enqueue(item: T): void {
  this.items.[1](item);
}

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

Apush

Bpop

Cshift

Dunshift

Attempts:

3 left

💡 Hint

Common Mistakes

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

Using shift or unshift changes the front of the queue, not the end.

The push method adds an element to the end of an array, which is how enqueue works in a queue.

2fill in blank

medium

Complete the code to check if the queue is empty before enqueueing.

DSA Typescript

enqueue(item: T): void {
  if (this.items.[1] === 0) {
  }
  this.items.push(item);
}

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

Asize

Bcount

Clength

Dlength()

Attempts:

3 left

💡 Hint

Common Mistakes

Using size or count which are not valid properties for arrays in TypeScript.

Using length() as a method instead of a property.

The length property gives the number of elements in an array in TypeScript.

3fill in blank

hard

Fix the error in the enqueue method to correctly add the item.

DSA Typescript

enqueue(item: T): void {
  this.items.[1](item);
}

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

Aadd

Bpush

Cinsert

Dappend

Attempts:

3 left

💡 Hint

Common Mistakes

Using add or append which are not valid array methods.

Using insert which is not a method on arrays.

The correct method to add an element at the end of an array in TypeScript is push.

4fill in blank

hard

Fill both blanks to enqueue an item and update the size property.

DSA Typescript

enqueue(item: T): void {
  this.items.[1](item);
  this.size = this.items.[2];
}

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

Apush

Blength

Cpop

Dsize

Attempts:

3 left

💡 Hint

Common Mistakes

Using pop instead of push removes an element.

Using size property on array which does not exist.

Use push to add the item and length to update the size of the queue.

5fill in blank

hard

Fill all three blanks to enqueue an item, update size, and print the queue length.

DSA Typescript

enqueue(item: T): void {
  this.items.[1](item);
  this.size = this.items.[2];
  console.log('Queue length:', this.items.[3]);
}

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

Apush

Blength

Dsize

Attempts:

3 left

💡 Hint

Common Mistakes

Using size property on array which does not exist.

Using pop or other methods that remove elements.

Use push to add the item, and length property to update size and print the queue length.

Practice

1. What does the enqueue operation do in a queue data structure?

easy

A. Adds an element to the end of the queue

B. Removes an element from the front of the queue

C. Checks if the queue is empty

D. Returns the size of the queue

Solution

1. Step 1: Understand the queue structure

   A queue works like a line where elements are added at the back and removed from the front.

2. Step 2: Define the enqueue operation

   Enqueue means adding a new element to the end of the queue, so it waits its turn.

3. Final Answer:

   Adds an element to the end of the queue -> Option A

4. Quick Check:

   Enqueue = Add at end [OK]

Hint: Enqueue means add at the back of the queue [OK]

Common Mistakes:

• Confusing enqueue with dequeue (removal)
• Thinking enqueue checks queue size
• Assuming enqueue removes elements

2. Which of the following is the correct TypeScript syntax to add an element 5 to a queue represented by an array queue?

easy

A. queue.pop(5);

B. queue.push(5);

C. queue.shift(5);

D. queue.unshift(5);

Solution

1. Step 1: Identify array methods for queue operations

   In TypeScript, push adds an element at the end, which matches enqueue.

2. Step 2: Match enqueue with correct method

   pop removes from end, shift removes from front, unshift adds at front. So only push adds at the end.

3. Final Answer:

   queue.push(5); -> Option B

4. Quick Check:

   Enqueue uses push() to add at end [OK]

Hint: Use push() to add at end of array for enqueue [OK]

Common Mistakes:

• Using pop() which removes instead of adds
• Using shift() or unshift() which affect front of queue
• Confusing push() with unshift()

3. What will be the state of the queue after executing the following TypeScript code?

let queue: number[] = [10, 20, 30];
queue.push(40);
queue.push(50);

medium

A. [10, 20, 30, 40, 50]

B. [50, 40, 10, 20, 30]

C. [10, 20, 30]

D. [40, 50]

Solution

1. Step 1: Start with initial queue

   The queue starts as [10, 20, 30].

2. Step 2: Apply enqueue operations

   First, push(40) adds 40 at the end: [10, 20, 30, 40]. Then push(50) adds 50 at the end: [10, 20, 30, 40, 50].

3. Final Answer:

   [10, 20, 30, 40, 50] -> Option A

4. Quick Check:

   push adds at end, final queue = [10,20,30,40,50] [OK]

Hint: push() adds elements at the end in order [OK]

Common Mistakes:

• Thinking push adds at front
• Ignoring second push operation
• Confusing push with pop or shift

4. Identify the error in the following TypeScript code that tries to enqueue an element 25 to a queue represented by an array queue:

let queue: number[] = [5, 10, 15];
queue.pop(25);

medium

A. The element 25 should be added using shift

B. pop adds element at the front, so wrong method

C. The queue array is not initialized properly

D. pop does not take arguments and removes from the end

Solution

1. Step 1: Understand pop() method behavior

   pop() removes the last element from the array and does not accept any arguments.

2. Step 2: Identify misuse of pop()

   Calling pop(25) is incorrect because pop() cannot add elements; it only removes.

3. Final Answer:

   pop does not take arguments and removes from the end -> Option D

4. Quick Check:

   pop() removes, push() adds [OK]

Hint: pop() removes last element; push() adds at end [OK]

Common Mistakes:

• Using pop() to add elements
• Confusing shift() and pop()
• Passing arguments to pop()

5. You have a queue implemented as an array in TypeScript. You want to enqueue multiple elements [100, 200, 300] at once while preserving order. Which code snippet correctly enqueues all elements in order?

hard

A. queue.unshift(100, 200, 300);

B. queue.push([100, 200, 300]);

C. queue.push(100, 200, 300);

D. queue.pop(100); queue.pop(200); queue.pop(300);

Solution

1. Step 1: Understand push with multiple arguments

   push() can take multiple arguments and adds them in order at the end of the array.

2. Step 2: Analyze each option

   queue.push(100, 200, 300); adds 100, 200, 300 in order at the end. queue.push([100, 200, 300]); adds a single array element, nesting the array. queue.unshift(100, 200, 300); adds elements at the front, reversing order. queue.pop(100); queue.pop(200); queue.pop(300); uses pop which removes elements, not adds.

3. Final Answer:

   queue.push(100, 200, 300); -> Option C

4. Quick Check:

   push(...items) adds all at end in order [OK]

Hint: Use push with multiple args to enqueue many elements [OK]

Common Mistakes:

• Using push with array argument nests array
• Using unshift adds at front, reversing order
• Using pop to add elements