Example 1: breadth first traversal python program
class Graph:
def __init__(self):
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 of graph in c
// BFS algorithm in C
struct queue {
int items[SIZE];
int front;
int rear;
};
struct queue* createQueue();
void enqueue(struct queue* q, int);
int dequeue(struct queue* q);
void display(struct queue* q);
int isEmpty(struct queue* q);
void printQueue(struct queue* q);
struct node {
int vertex;
struct node* next;
};
struct node* createNode(int);
struct Graph {
int numVertices;
struct node** adjLists;
int* visited;
};
// BFS algorithm
void bfs(struct Graph* graph, int startVertex) {
struct queue* q = createQueue();
graph->visited[startVertex] = 1;
enqueue(q, startVertex);
while (!isEmpty(q)) {
printQueue(q);
int currentVertex = dequeue(q);
printf("Visited %d\n", currentVertex);
struct node* temp = graph->adjLists[currentVertex];
while (temp) {
int adjVertex = temp->vertex;
if (graph->visited[adjVertex] == 0) {
graph->visited[adjVertex] = 1;
enqueue(q, adjVertex);
}
temp = temp->next;
}
}
}
// Creating a node
struct node* createNode(int v) {
struct node* newNode = malloc(sizeof(struct node));
newNode->vertex = v;
newNode->next = NULL;
return newNode;
}
// Creating a graph
struct Graph* createGraph(int vertices) {
struct Graph* graph = malloc(sizeof(struct Graph));
graph->numVertices = vertices;
graph->adjLists = malloc(vertices * sizeof(struct node*));
graph->visited = malloc(vertices * sizeof(int));
int i;
for (i = 0; i < vertices; i++) {
graph->adjLists[i] = NULL;
graph->visited[i] = 0;
}
return graph;
}
// Add edge
void addEdge(struct Graph* graph, int src, int dest) {
// Add edge from src to dest
struct node* newNode = createNode(dest);
newNode->next = graph->adjLists[src];
graph->adjLists[src] = newNode;
// Add edge from dest to src
newNode = createNode(src);
newNode->next = graph->adjLists[dest];
graph->adjLists[dest] = newNode;
}
// Create a queue
struct queue* createQueue() {
struct queue* q = malloc(sizeof(struct queue));
q->front = -1;
q->rear = -1;
return q;
}
// Check if the queue is empty
int isEmpty(struct queue* q) {
if (q->rear == -1)
return 1;
else
return 0;
}
// Adding elements into queue
void enqueue(struct queue* q, int value) {
if (q->rear == SIZE - 1)
printf("\nQueue is Full!!");
else {
if (q->front == -1)
q->front = 0;
q->rear++;
q->items[q->rear] = value;
}
}
// Removing elements from queue
int dequeue(struct queue* q) {
int item;
if (isEmpty(q)) {
printf("Queue is empty");
item = -1;
} else {
item = q->items[q->front];
q->front++;
if (q->front > q->rear) {
printf("Resetting queue ");
q->front = q->rear = -1;
}
}
return item;
}
// Print the queue
void printQueue(struct queue* q) {
int i = q->front;
if (isEmpty(q)) {
printf("Queue is empty");
} else {
printf("\nQueue contains \n");
for (i = q->front; i < q->rear + 1; i++) {
printf("%d ", q->items[i]);
}
}
}
int main() {
struct Graph* graph = createGraph(6);
addEdge(graph, 0, 1);
addEdge(graph, 0, 2);
addEdge(graph, 1, 2);
addEdge(graph, 1, 4);
addEdge(graph, 1, 3);
addEdge(graph, 2, 4);
addEdge(graph, 3, 4);
bfs(graph, 0);
return 0;
}