BFS Breadth First Search on Graph in DSA C - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to initialize the queue front index.

DSA C

int front = [1];

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A1

B0

C-1

DNULL

Attempts:

3 left

💡 Hint

Common Mistakes

Initializing front to -1 causes invalid array access like queue[front].

Using NULL is invalid for integer index.

The queue front index is initialized to 0 (with rear typically -1) to indicate the queue is empty.

2fill in blank

medium

Complete the code to enqueue a vertex into the queue.

DSA C

queue[++rear] = [1];

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Avertex

Bvisited

Cadjacency

Dfront

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'visited' instead of vertex causes wrong data in queue.

Using 'front' or 'adjacency' is incorrect for enqueue operation.

We enqueue the current vertex by placing it at the rear of the queue.

3fill in blank

medium

Fix the error in the BFS loop condition to continue while queue is not empty.

DSA C

while (front [1] rear) {

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A<

B>

C==

D<=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' misses the last element in the queue.

Using '==' only runs once and stops prematurely.

The loop continues while front is less than or equal to rear, meaning queue has elements.

4fill in blank

hard

Fill both blanks to mark a vertex as visited and enqueue it.

DSA C

if (!visited[adjacency[i]]) {
    visited[adjacency[i]] = [1];
    queue[++rear] = [2];
}

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

A1

B0

Cadjacency[i]

Di

Attempts:

3 left

💡 Hint

Common Mistakes

Setting visited to 0 means not visited.

Enqueueing 'i' instead of adjacency[i] adds wrong vertex.

Mark the adjacency vertex as visited by setting 1, then enqueue that vertex.

5fill in blank

hard

Fill all three blanks to print the BFS traversal order.

DSA C

for (int i = [1]; i [2] [3]; i++) {
    printf("%d ", queue[i]);
}

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

Afront

B<

Crear + 1

Drear

Attempts:

3 left

💡 Hint

Common Mistakes

Starting from front + 1 skips first element.

Using '<=' with rear + 1 causes out-of-bound access.

Start from front, go while i < rear + 1 to print all elements in queue.