Enqueue Operation in DSA Python - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

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

DSA Python

queue = [1, 2, 3]
queue.[1](4)
print(queue)

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

Aappend

Bpop

Cinsert

Dremove

Attempts:

3 left

💡 Hint

Common Mistakes

Using pop removes an element instead of adding.

Using insert requires an index and adds at that position.

The append method adds an element to the end of the list, which simulates enqueue in a queue.

2fill in blank

medium

Complete the code to enqueue the value 10 into the queue.

DSA Python

queue = []
value = 10
queue.[1](value)
print(queue)

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

Apop

Bremove

Cappend

Dinsert

Attempts:

3 left

💡 Hint

Common Mistakes

Using pop or remove which remove elements.

Using insert without specifying index.

To add a value to the end of the queue, use append.

3fill in blank

hard

Fix the error in the enqueue operation to add 5 to the queue.

DSA Python

queue = [1, 2, 3]
queue.[1](5)
print(queue)

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

Apop

Bappend

Cremove

Dinsert

Attempts:

3 left

💡 Hint

Common Mistakes

Using pop or remove instead of append.

Using insert without index.

The correct method to add an element at the end is append. Using pop or remove removes elements instead.

4fill in blank

hard

Fill both blanks to enqueue the value 7 into the queue and then print it.

DSA Python

queue = [4, 5, 6]
queue.[1]([2])
print(queue)

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

Aappend

Bpop

C7

Dremove

Attempts:

3 left

💡 Hint

Common Mistakes

Using pop or remove which remove elements.

Not providing the value to add.

Use append to add the value 7 to the queue.

5fill in blank

hard

Fill both blanks to enqueue the uppercase string 'HELLO' into the queue and then print it.

DSA Python

queue = ['a', 'b', 'c']
value = 'hello'
queue.[1](value[2]) 
print(queue)

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

Aappend

B.upper()

D.pop()

Attempts:

3 left

💡 Hint

Common Mistakes

Using pop instead of append.

Forgetting to convert to uppercase.

Adding extra characters in print.

Use append to add the value. Convert value to uppercase with .upper(). Print the queue as is.

Practice

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

easy

A. Returns the size of the queue

B. Removes an element from the front of the queue

C. Checks if the queue is empty

D. Adds an element to the end of the queue

Solution

1. Step 1: Understand the queue structure

   A queue works like a line where new elements join at the back.

2. Step 2: Define enqueue operation

   Enqueue means adding an element to the end of this line.

3. Final Answer:

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

4. Quick Check:

   Enqueue = Add to end [OK]

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

Common Mistakes:

• Confusing enqueue with dequeue
• Thinking enqueue removes elements
• Mixing enqueue with checking size

2. Which of the following is the correct syntax to enqueue an element 5 into a queue named q implemented as a Python list?

easy

A. q.enqueue(5)

B. q.push(5)

C. q.append(5)

D. q.insert(0, 5)

Solution

1. Step 1: Identify Python list method for adding at end

   Python lists use append() to add elements at the end.

2. Step 2: Match enqueue operation to list method

   Enqueue adds to the back, so q.append(5) is correct.

3. Final Answer:

   q.append(5) -> Option C

4. Quick Check:

   Enqueue in list = append() [OK]

Hint: Use append() to add at the end of a Python list [OK]

Common Mistakes:

• Using push() which is not a Python list method
• Using insert(0, 5) which adds at front
• Assuming enqueue is a built-in list method

3. What will be the output of the following code?

queue = []
queue.append(10)
queue.append(20)
queue.append(30)
print(queue)

medium

A. [30, 20, 10]

B. [10, 20, 30]

C. [10, 30, 20]

D. Error

Solution

1. Step 1: Trace each enqueue operation

   Appending 10, then 20, then 30 adds elements in order at the end.

2. Step 2: Check final queue state

   The list will be [10, 20, 30] after all appends.

3. Final Answer:

   [10, 20, 30] -> Option B

4. Quick Check:

   Appending in order = [10, 20, 30] [OK]

Hint: Appending adds elements in order at the end [OK]

Common Mistakes:

• Reversing the order of elements
• Thinking append adds at front
• Expecting an error due to empty list

4. Identify the error in the following enqueue implementation for a queue using a Python list:

def enqueue(queue, item):
    queue.insert(item)

q = [1, 2, 3]
enqueue(q, 4)
print(q)

medium

A. insert() requires two arguments: index and item

B. insert() cannot be used on lists

C. enqueue should use append() instead of insert()

D. queue is not defined

Solution

1. Step 1: Check insert() method usage

   Python list's insert() needs two arguments: position index and the item.

2. Step 2: Identify missing argument

   The code calls insert(item) with only one argument, causing an error.

3. Final Answer:

   insert() requires two arguments: index and item -> Option A

4. Quick Check:

   insert() needs index and item [OK]

Hint: insert() needs index and item arguments [OK]

Common Mistakes:

• Using insert() with one argument
• Confusing insert() with append()
• Ignoring Python method argument requirements

5. You have a queue implemented as a Python list. You want to enqueue multiple elements [7, 8, 9] at once while preserving order. Which code snippet correctly enqueues all elements in order?

hard

A. queue.extend([7, 8, 9])

B. for x in [7, 8, 9]:
queue.insert(0, x)

C. queue.append([7, 8, 9])

D. queue = [7, 8, 9] + queue

Solution

1. Step 1: Understand enqueue multiple elements

   Enqueue adds elements at the end preserving order.

2. Step 2: Analyze each option

   for x in [7, 8, 9]: queue.insert(0, x) inserts at front reversing order; queue.append([7, 8, 9]) appends list as single element; queue = [7, 8, 9] + queue prepends elements; queue.extend([7, 8, 9]) extends list adding elements in order at end.

3. Final Answer:

   queue.extend([7, 8, 9]) -> Option A

4. Quick Check:

   extend() adds multiple elements at end [OK]

Hint: Use extend() to add multiple elements at queue end [OK]

Common Mistakes:

• Using append() which nests list inside queue
• Using insert(0, x) which reverses order
• Prepending elements instead of appending