Graphs are one of the many data structures which are actually mathematical structures. A graph is a triplet of E,V,G; where E represents the set of edges, V represents the set of vertices, G represents a function linking the corresponding vertices to its edges. In this post, I will talk about graph traversals. But before that, lets first talk about how to represent a graph and then, we will talk about traversing a graph.
Graph representation:
readymade codes are:
#include <stdio.h>
#include <stdlib.h>
#define SIZE 40
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;
};
struct Graph* createGraph(int vertices);
void addEdge(struct Graph* graph, int src, int dest);
void printGraph(struct Graph* graph);
void bfs(struct Graph* graph, int startVertex);
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;
}
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;
}
}
}
struct node* createNode(int v)
{
struct node* newNode = malloc(sizeof(struct node));
newNode->vertex = v;
newNode->next = NULL;
return newNode;
}
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;
}
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;
}
struct queue* createQueue() {
struct queue* q = malloc(sizeof(struct queue));
q->front = -1;
q->rear = -1;
return q;
}
int isEmpty(struct queue* q) {
if(q->rear == -1)
return 1;
else
return 0;
}
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;
}
}
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;
}
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]);
}
}
}
Caution: these codes are not written by the site owner. These are
compiled to provide a full set of codes for data structure on this site.
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