用prime算法求无向连通网的最小生成树，第一行输入顶点数，第二行为起始顶点，接着输入各边，C语言

以下是用prime算法求无向连通网的最小生成树的C语言实现：

#include <stdio.h>
#include <stdlib.h>
#include <limits.h>

#define MAX_VERTICES 1000

typedef struct {
    int weight;
    int visited;
} Edge;

typedef struct {
    Edge edges[MAX_VERTICES][MAX_VERTICES];
    int num_vertices;
} Graph;

int get_min_edge(Graph* graph, int* distances) {
    int min_edge = -1;
    int min_distance = INT_MAX;
    for (int i = 0; i < graph->num_vertices; i++) {
        if (!graph->edges[i][i].visited && distances[i] < min_distance) {
            min_edge = i;
            min_distance = distances[i];
        }
    }
    return min_edge;
}

void print_mst(Graph* graph, int* parents) {
    printf("Minimum Spanning Tree:\n");
    for (int i = 1; i < graph->num_vertices; i++) {
        printf("(%d, %d) - %d\n", parents[i], i, graph->edges[i][parents[i]].weight);
    }
}

void prim(Graph* graph, int start_vertex) {
    int distances[MAX_VERTICES];
    int parents[MAX_VERTICES];
    for (int i = 0; i < graph->num_vertices; i++) {
        distances[i] = INT_MAX;
        parents[i] = -1;
    }
    distances[start_vertex] = 0;
    for (int i = 0; i < graph->num_vertices; i++) {
        int current_vertex = get_min_edge(graph, distances);
        if (current_vertex == -1) {
            break;
        }
        graph->edges[current_vertex][current_vertex].visited = 1;
        for (int j = 0; j < graph->num_vertices; j++) {
            if (graph->edges[current_vertex][j].weight > 0 && !graph->edges[j][j].visited && graph->edges[current_vertex][j].weight < distances[j]) {
                distances[j] = graph->edges[current_vertex][j].weight;
                parents[j] = current_vertex;
            }
        }
    }
    print_mst(graph, parents);
}

int main() {
    Graph graph;
    scanf("%d", &graph.num_vertices);
    int start_vertex;
    scanf("%d", &start_vertex);
    for (int i = 0; i < graph.num_vertices; i++) {
        for (int j = 0; j < graph.num_vertices; j++) {
            graph.edges[i][j].weight = 0;
            graph.edges[i][j].visited = 0;
        }
    }
    int num_edges;
    scanf("%d", &num_edges);
    for (int i = 0; i < num_edges; i++) {
        int vertex1, vertex2, weight;
        scanf("%d %d %d", &vertex1, &vertex2, &weight);
        graph.edges[vertex1][vertex2].weight = weight;
        graph.edges[vertex2][vertex1].weight = weight;
    }
    prim(&graph, start_vertex);
    return 0;
}

主要思路是使用一个一维数组`distances`来存储每个顶点到最小生成树的距离，然后每次选择距离最小的未访问过的顶点加入最小生成树，并更新`distances`数组。具体实现可以参考上述代码。