What is a breadth-first search (BFS) in C and how is it implemented?

Table of Contents

Introduction

Breadth-First Search (BFS) is a graph traversal algorithm used to explore nodes level by level. BFS is useful for finding the shortest path in unweighted graphs and is commonly employed in various applications such as network analysis and pathfinding. This guide covers the fundamentals of BFS, its implementation in C, and practical examples.

Understanding Breadth-First Search (BFS)

BFS systematically explores all nodes at the present depth level before moving on to nodes at the next depth level. It utilizes a queue to keep track of nodes that need to be explored. This approach ensures that BFS traverses nodes in the order of their distance from the starting node.

How BFS Works

  1. Initialization: Start by initializing a queue and marking the starting node as visited.
  2. Enqueue Starting Node: Add the starting node to the queue.
  3. Process Nodes: Dequeue a node from the front of the queue, process it, and enqueue all its adjacent (and not yet visited) nodes.
  4. Repeat: Continue this process until the queue is empty.

Implementation in C

Here’s a C implementation of BFS for a graph represented using an adjacency list:

Practical Examples

Example 1: Finding the Shortest Path in an Unweighted Graph

BFS can be used to find the shortest path between nodes in an unweighted graph. Each level of BFS represents a step in the shortest path.

Example 2: Level-Order Traversal of a Tree

In a tree, BFS can be used to traverse nodes level by level, which is useful for algorithms that need to process nodes at the same depth.

Conclusion

Breadth-First Search (BFS) is an essential algorithm for graph traversal, ensuring that nodes are explored level by level. Implementing BFS in C involves using a queue to manage node exploration and an adjacency matrix to represent the graph. Understanding BFS can enhance your ability to solve various graph-related problems efficiently.

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