This Python program checks if an undirected graph is bipartite using BFS and a color-coding approach. A bipartite graph can be divided into two sets of vertices such that no two vertices within the same set are connected by an edge.

In graph theory, a bipartite graph is a graph whose vertices can be divided into two disjoint sets such that no two vertices within the same set are adjacent. We can use the Breadth-First Search (BFS) algorithm to check if an undirected graph is bipartite.

## Problem Statement

Write a Python program to determine if an undirected graph is bipartite using BFS.

## Python Program to Check if Undirected Graph is Bipartite using BFS

from collections import defaultdict, deque class Graph: def __init__(self, vertices): self.graph = defaultdict(list) self.V = vertices def add_edge(self, u, v): self.graph[u].append(v) self.graph[v].append(u) def is_bipartite(self, src): color = [-1] * self.V color[src] = 1 queue = deque() queue.append(src) while queue: u = queue.popleft() for v in self.graph[u]: if color[v] == -1: color[v] = 1 - color[u] queue.append(v) elif color[v] == color[u]: return False return True def is_bipartite_graph(graph): g = Graph(len(graph)) for u, neighbors in enumerate(graph): for v in neighbors: g.add_edge(u, v) return g.is_bipartite(0) # Start BFS from the first vertex # Example usage: if __name__ == "__main__": graph = [[1, 3], [0, 2], [1, 3], [0, 2]] if is_bipartite_graph(graph): print("The given graph is bipartite.") else: print("The given graph is not bipartite.")

## How It Works

- We represent the graph as an adjacency list using defaultdict.
- We create a function
`is_bipartite`

that takes the source vertex as an argument and performs a BFS traversal of the graph while assigning colors (0 or 1) to vertices. - If at any point during BFS, we encounter an adjacent vertex with the same color as the current vertex, the graph is not bipartite, and we return
`False`

. - If the BFS traversal completes without any conflicts in vertex coloring, we return
`True`

. - The
`is_bipartite_graph`

function converts the given graph into the`Graph`

class and starts BFS from the first vertex.