/* Breadth First Search (BFS) - menu driven (same structure as the lab program) */ /* printf and scanf live here */ #include /* MAX = largest number of vertices */ #define MAX 20 /* Adjacency matrix: graph[i][j] = 1 means an edge between i and j */ int graph[MAX][MAX]; /* visited[i] = 1 once vertex i has been reached */ int visited[MAX]; /* n = number of vertices, created = 1 once a graph has been entered */ int n, created = 0; /* CREATE: read the number of vertices and the adjacency matrix */ void createGraph() { int i, j; printf("Enter number of vertices (1-%d): ", MAX); scanf("%d", &n); /* Reject a size outside 1 to MAX */ if (n < 1 || n > MAX) { printf("Invalid number of vertices.\n"); created = 0; return; } printf("Enter adjacency matrix (%d x %d):\n", n, n); /* Row i of the matrix */ for (i = 0; i < n; i++) { /* Column j of this row */ for (j = 0; j < n; j++) { scanf("%d", &graph[i][j]); } } created = 1; printf("Graph created successfully.\n"); } /* DISPLAY: print the matrix row by row */ void displayGraph() { int i, j; if (!created) { printf("Please create the graph first.\n"); return; } printf("\nAdjacency Matrix:\n"); for (i = 0; i < n; i++) { for (j = 0; j < n; j++) { printf("%d ", graph[i][j]); } printf("\n"); } } /* BFS = visit level by level, using a QUEUE */ void BFS(int start) { /* Local queue: front = next to remove, rear = next free slot */ int queue[MAX]; int front = 0, rear = 0; int i, vertex; /* Clear visited[] so the search can be repeated */ for (i = 0; i < n; i++) visited[i] = 0; /* Mark visited when a vertex is ENQUEUED, then enqueue the start vertex */ visited[start] = 1; queue[rear++] = start; printf("BFS Traversal: "); /* Repeat while the queue is not empty */ while (front < rear) { /* Dequeue the next vertex and print it */ vertex = queue[front++]; printf("%d ", vertex); for (i = 0; i < n; i++) { /* Edge exists and the neighbour is not visited yet */ if (graph[vertex][i] == 1 && visited[i] == 0) { visited[i] = 1; /* Enqueue the unvisited neighbour */ queue[rear++] = i; } } } printf("\n"); } /* Program starts here */ int main() { int choice, start; /* Menu repeats until Exit is chosen */ do { printf("\n----- BFS MENU -----\n"); printf("1. Create Graph\n"); printf("2. Display Graph\n"); printf("3. Perform BFS Traversal\n"); printf("4. Exit\n"); printf("Enter your choice: "); scanf("%d", &choice); /* Run the code for the chosen option */ switch (choice) { /* Option 1: read the graph */ case 1: createGraph(); break; /* Option 2: show the matrix */ case 2: displayGraph(); break; /* Option 3: traverse (a graph must exist first) */ case 3: if (!created) { printf("Please create the graph first.\n"); break; } printf("Enter starting vertex (0 to %d): ", n - 1); scanf("%d", &start); if (start < 0 || start >= n) { printf("Invalid starting vertex.\n"); break; } BFS(start); break; /* Option 4: exit (loop ends when choice == 4) */ case 4: printf("Program terminated.\n"); break; default: printf("Invalid choice. Try again.\n"); } } while (choice != 4); return 0; }