bfs traversal algorithm code example

Example 1: breadth first traversal python program

class Graph:
    def __init__(self):
        # dictionary containing keys that map to the corresponding vertex object
        self.vertices = {}
 
    def add_vertex(self, key):
        """Add a vertex with the given key to the graph."""
        vertex = Vertex(key)
        self.vertices[key] = vertex
 
    def get_vertex(self, key):
        """Return vertex object with the corresponding key."""
        return self.vertices[key]
 
    def __contains__(self, key):
        return key in self.vertices
 
    def add_edge(self, src_key, dest_key, weight=1):
        """Add edge from src_key to dest_key with given weight."""
        self.vertices[src_key].add_neighbour(self.vertices[dest_key], weight)
 
    def does_edge_exist(self, src_key, dest_key):
        """Return True if there is an edge from src_key to dest_key."""
        return self.vertices[src_key].does_it_point_to(self.vertices[dest_key])
 
    def __iter__(self):
        return iter(self.vertices.values())
 
 
class Vertex:
    def __init__(self, key):
        self.key = key
        self.points_to = {}
 
    def get_key(self):
        """Return key corresponding to this vertex object."""
        return self.key
 
    def add_neighbour(self, dest, weight):
        """Make this vertex point to dest with given edge weight."""
        self.points_to[dest] = weight
 
    def get_neighbours(self):
        """Return all vertices pointed to by this vertex."""
        return self.points_to.keys()
 
    def get_weight(self, dest):
        """Get weight of edge from this vertex to dest."""
        return self.points_to[dest]
 
    def does_it_point_to(self, dest):
        """Return True if this vertex points to dest."""
        return dest in self.points_to
 
 
class Queue:
    def __init__(self):
        self.items = []
 
    def is_empty(self):
        return self.items == []
 
    def enqueue(self, data):
        self.items.append(data)
 
    def dequeue(self):
        return self.items.pop(0)
 
 
def display_bfs(vertex):
    """Display BFS Traversal starting at vertex."""
    visited = set()
    q = Queue()
    q.enqueue(vertex)
    visited.add(vertex)
    while not q.is_empty():
        current = q.dequeue()
        print(current.get_key(), end=' ')
        for dest in current.get_neighbours():
            if dest not in visited:
                visited.add(dest)
                q.enqueue(dest)
 
 
g = Graph()
print('Menu')
print('add vertex <key>')
print('add edge <src> <dest>')
print('bfs <vertex key>')
print('display')
print('quit')
 
while True:
    do = input('What would you like to do? ').split()
 
    operation = do[0]
    if operation == 'add':
        suboperation = do[1]
        if suboperation == 'vertex':
            key = int(do[2])
            if key not in g:
                g.add_vertex(key)
            else:
                print('Vertex already exists.')
        elif suboperation == 'edge':
            src = int(do[2])
            dest = int(do[3])
            if src not in g:
                print('Vertex {} does not exist.'.format(src))
            elif dest not in g:
                print('Vertex {} does not exist.'.format(dest))
            else:
                if not g.does_edge_exist(src, dest):
                    g.add_edge(src, dest)
                else:
                    print('Edge already exists.')
 
    elif operation == 'bfs':
        key = int(do[1])
        print('Breadth-first Traversal: ', end='')
        vertex = g.get_vertex(key)
        display_bfs(vertex)
        print()
 
    elif operation == 'display':
        print('Vertices: ', end='')
        for v in g:
            print(v.get_key(), end=' ')
        print()
 
        print('Edges: ')
        for v in g:
            for dest in v.get_neighbours():
                w = v.get_weight(dest)
                print('(src={}, dest={}, weight={}) '.format(v.get_key(),
                                                             dest.get_key(), w))
        print()
 
    elif operation == 'quit':
        break

Example 2: bfs traversal code

#include <bits/stdc++.h>
using namespace std;
#define ll  long long int
#define ull unsigned long long int
void addedge(vector<int>adj[],int u,int v)
{
    adj[u].push_back(v);
    adj[v].push_back(u);
}
void print_list(vector <int> adj[],int n)
{
    for(int i=0;i<n;i++)
    {
        cout << "adjacency list for node" << i << "is :\n";
        for(auto ele: adj[i])
        {
            cout << "->" << ele << " \n";
        }

    }
}
void BFS(int v,int e,vector<int>adj[])
{
    bool visited[e];
    for(int i=0;i<e;i++)
    {
        visited[i]= false;
    }
    list<int>queue;
    visited[v]= true;
    queue.push_back(v);
    while (!queue.empty())
    {
        v = queue.front();
        cout << v << " ";
        queue.pop_front();
        for(auto ele:adj[v])
        {
            if(!visited[ele])
            {
                visited[ele]= true;
                queue.push_back(ele);

            }
        }
    }
}


int main()
{
    int n,e;
    cin >> n >> e;
    vector <int> adj[n];
    int u,v;
    for(int i=0;i<e;i++)
    {

        cin >> u >> v;
        addedge(adj,u,v);

    }
    print_list(adj,n);
    BFS(v,e,adj);


    return 0;
}