prims.c

//Prim's algorithm for minimum spanning tree
#include <stdio.h>
#include <limits.h>
#include <stdbool.h>
#define V 5

int minKey(int key[], bool mstSet[])
{
	int min = INT_MAX, min_index;

	for (int v = 0; v < V; v++)
		if (mstSet[v] == false && key[v] < min)
			min = key[v], min_index = v;

	return min_index;
}

int printMST(int parent[], int graph[V][V])
{
	printf("Edge \tWeight\n");
	for (int i = 1; i < V; i++)
		printf("%d - %d \t%d \n", parent[i], i,
			graph[i][parent[i]]);
}

void primMST(int graph[V][V])
{
	int parent[V];
	int key[V];
	bool mstSet[V];

	for (int i = 0; i < V; i++)
		key[i] = INT_MAX, mstSet[i] = false;

	key[0] = 0;
	parent[0] = -1;

	for (int count = 0; count < V - 1; count++) {
	
		int u = minKey(key, mstSet);
		mstSet[u] = true;

		for (int v = 0; v < V; v++)

			if (graph[u][v] && mstSet[v] == false
				&& graph[u][v] < key[v])
				parent[v] = u, key[v] = graph[u][v];
	}

	printMST(parent, graph);
}

int main()
{
	
	int graph[V][V] = { { 0, 2, 0, 6, 0 },
						{ 2, 0, 3, 8, 5 },
						{ 0, 3, 0, 0, 7 },
						{ 6, 8, 0, 0, 9 },
						{ 0, 5, 7, 9, 0 } };

	primMST(graph);

	return 0;
}