DFS vs BFS: Difference Between DFS and BFS

# DFS vs BFS: Difference Between DFS and BFS

Last updated:
3rd Sep, 2023
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## What is BFS?

BFS, or Breadth-First Search, is a widely used algorithm in computer science and graph theory. It explores data structures systematically and efficiently by visiting neighboring vertices in a breadth-first manner, ensuring all nodes at the same distance from the source are visited before going deeper.

BFS guarantees the shortest path in an unweighted graph, but may not be the most efficient for complex scenarios or large datasets. Implemented using a queue data structure, BFS is a fundamental tool for exploring and analyzing graph-like structures in various computer science domains.

## Example of BFS

Let’s consider a different example to illustrate how BFS works. Here’s a visual representation of the graph:

Suppose we want to find the shortest path between person A and person F using BFS. We start the BFS algorithm from node A:

• Start at A (source vertex).
• Visit all immediate neighbors of A (B and C).
• Add B and C to the queue to explore their neighbors later.
• Queue: [B, C]
• Take the next vertex from the queue (B).
• Visit all immediate neighbors of B (A, D, and E).
• Add D and E to the queue since they haven’t been visited yet.
• Queue: [C, D, E]
• Take the next vertex from the queue (C).
• Visit all immediate neighbors of C (A and D).
• A has already been visited, so we skipped it.
• Queue: [D, E]
• Take the next vertex from the queue (D).
• Visit all immediate neighbors of D (B and C).
• Both B and C have already been visited, so we skipped them.
• Queue: [E]
• Take the next vertex from the queue (E).
• Visit all immediate neighbors of E (B and F).
• Queue: [F]
• Take the next vertex from the queue (F).
• F is the destination vertex we were looking for, so the BFS ends.
• The shortest path from A to F is: A -> B -> E -> F

In this example, BFS explored the graph layer by layer, ensuring that the shortest path between A and F was found. This property of BFS makes it particularly useful in applications like network routing and most straightforward path problems.

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## What is DFS?

DFS, or Depth-First Search, is an algorithm that explores graphs by moving deeply into a branch before backtracking to explore other branches. It uses a stack to track vertices and efficiently visits reachable vertices from a source.

While useful for certain graph-related problems like cycle detection and maze exploration, DFS does not guarantee to find the shortest path between nodes, as it may explore farther branches first. Nonetheless, DFS remains a crucial tool in computer science for various challenges involving graph-like structures.

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## Example of DFS

Let’s use DFS to traverse and explore the following undirected graph starting from the source vertex ‘A’:

DFS works as follows:

• Start at vertex ‘A’:

(Note: The asterisk ‘*’ denotes the current vertex being explored.)

• Visit an unvisited neighbor of ‘A,’ such as ‘B’:

• Visit an unvisited neighbor of ‘B,’ such as ‘E’:

• Visit an unvisited neighbor of ‘E.’ However, all neighbors of ‘E’ have already been visited, so backtrack:

• Backtrack to vertex ‘D’ and visit its unvisited neighbor, ‘C’:

• Since ‘C’ has no unvisited neighbors, backtrack again to vertex ‘D’:

• Now visit the last unvisited neighbor of ‘D,’ which is ‘F’:

• ‘F’ has no unvisited neighbors, and the stack is now empty, so the DFS process ends.
• The order of exploration in DFS is: A -> B -> E -> D -> C -> F

DFS explores as far as possible along each branch before backtracking, making it a useful algorithm for graph-related problems such as finding connected components, detecting cycles, and solving puzzles or maze exploration.

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## What is DRAM

DRAM stands for Dynamic Random-Access Memory, a common type of computer memory used for fast data access. It stores data and instructions needed by the processor. Unlike static RAM, DRAM is dynamic and requires periodic refreshing to maintain stored data. It offers cost-effective, high-capacity memory, making it suitable for computers’ main memory (RAM).

DRAM’s random-access nature enables quick data retrieval and modification, supporting smooth computing experiences. However, it consumes more power than SRAM and has slightly slower access times than cache memory. Overall, DRAM is critical in ensuring efficient data processing in modern computing devices. With its ability to provide cost-effective, high-capacity memory, DRAM remains a crucial component in the seamless performance of various computing tasks, from running applications to multitasking on personal computers and other electronic devices.

## BFS vs DFS: Difference between DFS and BFS.

Discover the power of graph traversal with BFS vs DFS in AI! Here’s a table highlighting the main difference between DFS and BFS in Artificial Intelligence:

 Aspect Depth-First Search (DFS) Breadth-First Search (BFS) Approach Explores as deep as possible before backtracking. Explores all immediate neighbors before moving to deeper levels. Data Structure Used Utilizes a stack data structure for tracking nodes. Uses a queue data structure for tracking nodes. Implementation Can be implemented using recursion or an explicit stack. Implemented using a queue for efficient node tracking. Memory Usage Requires less memory as it traverses one branch at a time. Requires more memory to maintain the queue for all neighbors. Completeness May not find the shortest path between two nodes. Guarantees finding the shortest path between two nodes. Use Cases Suitable for exploring deep paths and backtracking scenarios. Effective for finding the shortest path and connectivity analysis. Applications Solving puzzles, maze exploration, detecting cycles, and connectivity checks. Shortest path finding, network routing, web crawling, and level-order tree traversal.

DFS and BFS are two common graph traversal algorithms, each with its strengths and weaknesses. The choice between them depends on the specific problem and the desired outcomes regarding pathfinding and exploration strategies. Both BFS and DFS in data structure are essential graph traversal techniques that help explore and analyze different types of data structures in computer science and artificial intelligence.

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## BFS and DFS Algorithm in Data Structure

Breadth First Search and Depth First Search are fundamental graph traversal algorithms used in data structures to explore and analyze graphs or tree-like structures.

BFS starts from a designated source node and explores all immediate neighbors before moving to their neighbors. It utilizes a queue data structure to keep track of nodes to be visited, ensuring a level-by-level exploration. BFS guarantees finding the shortest path between the source and any reachable node, making it suitable for finding connected components, web crawling, and shortest path problems.

On the other hand, DFS explores as deep as possible along a branch before backtracking and exploring other branches. It employs a stack (recursion or explicit stack) to keep track of nodes to be explored. DFS is efficient for tasks involving exploring deep paths, backtracking, and finding graph cycles.

Both algorithms have specific applications and benefits, and the choice between BFS and DFS depends on the specific problem and the desired characteristics of the exploration process. Unlock the world of creativity and innovation with the Advanced Certificate Program in GenerativeAI. This program will equip you with cutting-edge skills to explore the fascinating realm of Generative AI and unleash your potential as an AI innovator.

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## Conclusion

The main difference between Depth-First Search (DFS) and Breadth-First Search (BFS) lies in their exploration strategies. DFS explores as deep as possible along a branch before backtracking, utilizing a stack data structure (either through recursion or an explicit stack). It is efficient for tasks involving deep path exploration, backtracking, and detecting cycles in graphs.

On the other hand, BFS explores all immediate neighbors before moving to deeper levels, using a queue data structure. It guarantees finding the shortest path between the source and any reachable node, making it suitable for finding connected components and shortest path problems.

The choice between DFS and BFS depends on the specific problem and the desired exploration characteristics. DFS is beneficial for tasks involving deep exploration and backtracking, while BFS is effective for finding the shortest paths and analyzing connectivity in graphs. Start your transformative journey with the Executive PG Program in Data Science & Machine Learning from the University of Maryland.

## FAQs

#### Pavan Vadapalli

Blog Author
Director of Engineering @ upGrad. Motivated to leverage technology to solve problems. Seasoned leader for startups and fast moving orgs. Working on solving problems of scale and long term technology strategy.
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## Frequently Asked Questions (FAQs)

1How do DFS and BFS algorithms differ in their traversal strategies?

In DFS, the algorithm explores as far as possible along a branch before backtracking to explore other branches, while in BFS, it systematically explores all immediate neighbors at the current level before moving on to deeper levels. The key difference lies in the order of exploration, making each algorithm suitable for different scenarios and applications.

2In AI, when would you prefer to use BFS over DFS, and vice versa?

Use BFS to find the shortest path between two nodes or explore all immediate neighbors in a systematic order. Use DFS for tasks involving deep exploration, like backtracking and solving puzzles.

3In terms of space complexity, which algorithm, DFS or BFS, is more efficient?

DFS typically requires less memory as it traverses one branch at a time, making it more space-efficient than BFS, which requires more memory to maintain the queue for all neighbors. DFS typically requires less memory as it traverses one branch at a time, making it more space-efficient than BFS, which requires more memory to maintain the queue for all neighbors.

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