Breadth First Search Quiz

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| Questions: 15 | Updated: Apr 30, 2026
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1. What data structure is primarily used in Breadth First Search?

Explanation

Breadth First Search (BFS) explores nodes level by level, visiting all neighbors of a node before moving deeper. A queue is ideal for this process, as it follows the First In, First Out (FIFO) principle, allowing the algorithm to process nodes in the order they are discovered, ensuring that all nodes at the current level are explored before moving to the next.

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About This Quiz
Breadth First Search Quiz - Quiz

This Breadth First Search Quiz tests your understanding of BFS as a graph traversal algorithm. You'll explore how BFS explores vertices level by level, its applications in shortest-path finding, and how it differs from depth-first search. Master the queue-based mechanics and real-world uses of this essential algorithm.

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2. In BFS, vertices are visited in order of their ______ from the source vertex.

Explanation

In Breadth-First Search (BFS), vertices are explored layer by layer, starting from the source vertex. Each layer corresponds to vertices that are equidistant from the source, ensuring that all nodes at a given distance are visited before moving on to nodes at the next greater distance. This systematic approach guarantees the shortest path in unweighted graphs.

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3. Which of the following is a correct order for BFS traversal starting from vertex A in graph A→B, A→C, B→D, C→D?

Explanation

In a Breadth-First Search (BFS) traversal, nodes are explored level by level. Starting from vertex A, the algorithm first visits its immediate neighbors B and C. Then, from B, it visits D. This results in the order A, B, C, D, reflecting the systematic exploration of adjacent nodes before moving deeper into the graph.

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4. True or False: BFS always finds the shortest path in an unweighted graph.

Explanation

BFS, or Breadth-First Search, explores all neighbors at the present depth prior to moving on to nodes at the next depth level. In an unweighted graph, this guarantees that the first time a node is reached, it is via the shortest path, making BFS an effective algorithm for finding the shortest path in such graphs.

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5. When using BFS, a vertex is marked as visited to prevent ______ processing.

Explanation

In Breadth-First Search (BFS), marking a vertex as visited prevents it from being processed multiple times. This ensures that each vertex is explored only once, maintaining the efficiency of the algorithm and avoiding infinite loops in cyclic graphs. It also helps in accurately determining the shortest path in unweighted graphs.

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6. What is the time complexity of BFS for a graph with V vertices and E edges?

Explanation

BFS (Breadth-First Search) explores each vertex and edge in a graph. It visits all V vertices and traverses each of the E edges once, leading to a total time complexity of O(V + E). This accounts for both the vertices and the edges, making it efficient for graph traversal.

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7. In BFS, which vertices are explored before moving to the next level?

Explanation

In Breadth-First Search (BFS), the algorithm explores all neighbors of the current vertex before proceeding to the next level. This ensures that all vertices at the same distance from the starting point are visited before moving deeper into the graph, maintaining a level-order traversal.

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8. True or False: BFS uses recursion as its primary mechanism for graph traversal.

Explanation

BFS, or Breadth-First Search, primarily uses an iterative approach with a queue to explore nodes level by level. Unlike DFS (Depth-First Search), which relies on recursion to traverse deeper into the graph, BFS systematically visits all neighboring nodes before moving on, making recursion unnecessary for its implementation.

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9. BFS is commonly used to find the shortest path in ______ graphs.

Explanation

BFS, or Breadth-First Search, explores all neighbors at the present depth prior to moving on to nodes at the next depth level. This characteristic ensures that it finds the shortest path in unweighted graphs, where all edges have the same weight, as it examines all possible paths level by level.

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10. Which algorithm explores vertices in a depth-first manner, opposite to BFS?

Explanation

Depth First Search (DFS) explores vertices by diving deep into a branch before backtracking, contrasting with Breadth-First Search (BFS), which explores all neighbors at the present depth prior to moving on. This depth-oriented approach allows DFS to efficiently traverse complex structures like trees and graphs.

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11. In BFS, the queue is used to store vertices that need to be ______.

Explanation

In Breadth-First Search (BFS), a queue is utilized to manage the vertices that have been discovered but not yet examined. This ensures that vertices are processed in the order they are encountered, allowing BFS to systematically explore each level of the graph before moving deeper, ensuring an efficient traversal of all reachable nodes.

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12. What happens to a vertex after it is dequeued in BFS?

Explanation

In Breadth-First Search (BFS), when a vertex is dequeued, it is marked as visited to avoid reprocessing. Simultaneously, its unvisited neighbors are enqueued for future exploration. This dual action ensures that all reachable vertices are systematically explored while preventing cycles and redundant checks.

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13. BFS is ideal for finding connected components in an ______ graph.

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14. True or False: BFS requires less memory than DFS for storing unvisited vertices.

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15. Which of the following is NOT a typical application of BFS?

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What data structure is primarily used in Breadth First Search?
In BFS, vertices are visited in order of their ______ from the source...
Which of the following is a correct order for BFS traversal starting...
True or False: BFS always finds the shortest path in an unweighted...
When using BFS, a vertex is marked as visited to prevent ______...
What is the time complexity of BFS for a graph with V vertices and E...
In BFS, which vertices are explored before moving to the next level?
True or False: BFS uses recursion as its primary mechanism for graph...
BFS is commonly used to find the shortest path in ______ graphs.
Which algorithm explores vertices in a depth-first manner, opposite to...
In BFS, the queue is used to store vertices that need to be ______.
What happens to a vertex after it is dequeued in BFS?
BFS is ideal for finding connected components in an ______ graph.
True or False: BFS requires less memory than DFS for storing unvisited...
Which of the following is NOT a typical application of BFS?
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