prim's algo P5
#include <stdio.h>
#include <limits.h>
#define V_MAX 100 // Maximum number of vertices
// Function to find the vertex with the minimum key value, from the set of vertices not yet included in the MST
int minKey(int key[], int mstSet[], int V) {
int min = INT_MAX, min_index;
for (int v = 0; v < V; v++)
if (mstSet[v] == 0 && key[v] < min)
min = key[v], min_index = v;
return min_index;
}
// Function to print the constructed MST stored in parent[]
void printMST(int parent[], int V, int graph[V_MAX][V_MAX]) {
printf("Edge Weight\n");
for (int i = 1; i < V; i++)
printf("%d - %d %d \n", parent[i], i, graph[i][parent[i]]);
}
// Function to construct and print MST for a graph represented using adjacency matrix representation
void primMST(int graph[][V_MAX], int V) {
int parent[V_MAX]; // Array to store constructed MST
int key[V_MAX]; // Key values used to pick minimum weight edge in cut
int mstSet[V_MAX]; // To represent set of vertices not yet included in MST
// Initialize all keys as INFINITE, mstSet[] as 0
for (int i = 0; i < V; i++) {
key[i] = INT_MAX;
mstSet[i] = 0;
}
// Always include first vertex in MST. Make key 0 so that this vertex is picked as the first vertex
key[0] = 0;
parent[0] = -1; // First node is always the root of MST
// The MST will have V vertices
for (int count = 0; count < V - 1; count++) {
// Pick the minimum key vertex from the set of vertices not yet included in MST
int u = minKey(key, mstSet, V);
// Add the picked vertex to the MST set
mstSet[u] = 1;
// Update key value and parent index of the adjacent vertices of the picked vertex
// Consider only those vertices which are not yet included in the MST
for (int v = 0; v < V; v++)
if (graph[u][v] && mstSet[v] == 0 && graph[u][v] < key[v])
parent[v] = u, key[v] = graph[u][v];
}
// Print the constructed MST
printMST(parent, V, graph);
}
int main() {
int V, E;
printf("Enter the number of vertices and edges: ");
scanf("%d %d", &V, &E);
if (V > V_MAX) {
printf("Error: Number of vertices exceeds the maximum limit.\n");
return 1;
}
// Create the graph as an adjacency matrix
int graph[V_MAX][V_MAX];
for (int i = 0; i < V; i++) {
for (int j = 0; j < V; j++) {
graph[i][j] = 0; // Initialize the graph with 0s
}
}
// Prompt the user to enter the source vertex, destination vertex, and weight for each edge
printf("Enter the source vertex, destination vertex, and weight for each edge:\n");
for (int i = 0; i < E; i++) {
int source, dest, weight;
scanf("%d %d %d", &source, &dest, &weight);
graph[source][dest] = weight;
graph[dest][source] = weight; // Since the graph is undirected
}
// Print the MST using Prim's algorithm
primMST(graph, V);
return 0;
}
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