Enqueue Operation in DSA C# - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

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

DSA C#

queue.[1](item);

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

APush

BAddFirst

CEnqueue

DInsert

Attempts:

3 left

💡 Hint

Common Mistakes

Using Push which is for stacks, not queues.

Using AddFirst which is for linked lists.

The Enqueue method adds an element to the end of the queue.

2fill in blank

medium

Complete the code to create a new queue of integers.

DSA C#

Queue<int> queue = new Queue<[1]>();

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

Aint

Bdouble

Cstring

Dchar

Attempts:

3 left

💡 Hint

Common Mistakes

Using string which is for text, not numbers.

Using double which is for decimal numbers.

We want a queue of integers, so the type parameter should be int.

3fill in blank

hard

Fix the error in the enqueue operation code.

DSA C#

queue.[1](5);

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

AEnqueue

BInsert

CAdd

DPush

Attempts:

3 left

💡 Hint

Common Mistakes

Using Add which is not a queue method.

Using Push which is for stacks.

The correct method to add an element to a queue is Enqueue. Other methods like Add or Push are not valid for queues.

4fill in blank

hard

Fill both blanks to enqueue a string element into the queue.

DSA C#

Queue<[1]> queue = new Queue<[2]>();
queue.Enqueue("hello");

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

Astring

Bint

Cdouble

Dchar

Attempts:

3 left

💡 Hint

Common Mistakes

Using different types in declaration and initialization.

Using numeric types when enqueuing strings.

To enqueue a string, the queue must be of type string in both declaration and initialization.

5fill in blank

hard

Fill all three blanks to enqueue multiple elements in a loop.

DSA C#

Queue<int> queue = new Queue<int>();
for (int [1] = 0; [2] < 3; [3]++) {
    queue.Enqueue([1]);
}

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

Ai

Bj

Ck

Dx

Attempts:

3 left

💡 Hint

Common Mistakes

Using different variable names in the loop parts.

Using variables not declared in the loop.

The loop variable is i used consistently in initialization, condition, and increment.

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 queue behavior

   A queue works like a line where new people join at the end.

2. Step 2: Define enqueue operation

   Enqueue means adding a new element at the back of the queue.

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
• Thinking enqueue removes elements
• Mixing enqueue with checking size

2. Which of the following is the correct syntax to enqueue an integer value 10 into a Queue<int> named q in C#?

easy

A. q.Enqueue(10);

B. q.Add(10);

C. q.Push(10);

D. q.Insert(10);

Solution

1. Step 1: Recall C# Queue method

   The method to add elements in Queue<T> is Enqueue.

2. Step 2: Match syntax

   Calling q.Enqueue(10); adds 10 to the queue correctly.

3. Final Answer:

   q.Enqueue(10); -> Option A

4. Quick Check:

   Use Enqueue() to add in C# Queue [OK]

Hint: Use Enqueue() method to add elements in C# Queue [OK]

Common Mistakes:

• Using Add() which is not in Queue
• Using Push() which is for stacks
• Using Insert() which is not a Queue method

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

Queue<string> q = new Queue<string>();
q.Enqueue("apple");
q.Enqueue("banana");
q.Enqueue("cherry");
Console.WriteLine(string.Join(", ", q));

medium

A. cherry, banana, apple

B. apple, banana, cherry

C. banana, cherry, apple

D. apple, cherry, banana

Solution

1. Step 1: Trace enqueue order

   Elements are added in order: apple, then banana, then cherry.

2. Step 2: Understand queue order

   Queue keeps order of insertion, so printing shows apple, banana, cherry.

3. Final Answer:

   apple, banana, cherry -> Option B

4. Quick Check:

   Queue prints in enqueue order [OK]

Hint: Queue keeps insertion order; output matches enqueue sequence [OK]

Common Mistakes:

• Assuming reverse order output
• Mixing enqueue with stack behavior
• Confusing output order with dequeue

4. Identify the error in the following code snippet that tries to enqueue an element into a queue:

Queue<int> q = new Queue<int>();
q.Enqueue(5);
q.Enqueue(10);
q.Enqueue(15);
q.Enqueue();

medium

A. Cannot enqueue integer values

B. Queue is not initialized

C. Enqueue method does not exist

D. Missing argument in the last Enqueue call

Solution

1. Step 1: Check method calls

   The last call q.Enqueue(); has no argument, but Enqueue requires one.

2. Step 2: Confirm method signature

   Enqueue needs a value to add, so missing argument causes error.

3. Final Answer:

   Missing argument in the last Enqueue call -> Option D

4. Quick Check:

   Enqueue requires one argument [OK]

Hint: Enqueue always needs one argument to add [OK]

Common Mistakes:

• Calling Enqueue without argument
• Assuming Enqueue can be empty
• Confusing initialization errors

5. You have a queue q with elements [1, 2, 3]. You want to enqueue elements 4 and 5, but only if the queue size is less than 5. Which code snippet correctly performs this conditional enqueue operation in C#?

hard

A. if (q.Count == 5) { q.Enqueue(4); q.Enqueue(5); }

B. if (q.Count <= 5) { q.Enqueue(4); q.Enqueue(5); }

C. if (q.Count < 5) { q.Enqueue(4); q.Enqueue(5); }

D. if (q.Count > 5) { q.Enqueue(4); q.Enqueue(5); }

Solution

1. Step 1: Understand queue size condition

   We want to add only if size is less than 5, so condition is q.Count < 5.

2. Step 2: Apply enqueue calls inside condition

   If condition is true, enqueue 4 and 5 to add them safely.

3. Final Answer:

   if (q.Count < 5) { q.Enqueue(4); q.Enqueue(5); } -> Option C

4. Quick Check:

   Use < 5 to check size before enqueue [OK]

Hint: Check queue size with Count before enqueueing [OK]

Common Mistakes:

• Using <= instead of < causing overflow
• Using > or == which are wrong conditions
• Not checking size before enqueue