c语言代码最短路径Dijkstra算法要求1. 实现最短路径算法 2. 避开一个指定点 3. 必经一个指定点 4. 推广到多个点

好的，以下是使用C语言实现Dijkstra算法并满足题目要求的代码：

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

#define MAX_VERTICES 100
#define INF INT_MAX

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

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

void create_graph(Graph *G, int n)
{
    int i, j;

    G->num_vertices = n;

    for (i = 0; i < n; i++)
        for (j = 0; j < n; j++)
            G->edges[i][j].weight = INF;
}

void add_edge(Graph *G, int u, int v, int weight)
{
    G->edges[u][v].weight = weight;
}

int get_min_distance(int dist[], int visited[], int n)
{
    int i, min = INF, min_index;

    for (i = 0; i < n; i++) {
        if (!visited[i] && dist[i] <= min) {
            min = dist[i];
            min_index = i;
        }
    }

    return min_index;
}

void dijkstra(Graph *G, int src, int dest, int avoid, int via)
{
    int i, j, u, alt;
    int dist[MAX_VERTICES];
    int visited[MAX_VERTICES];
    int prev[MAX_VERTICES];
    int avoid_visited[MAX_VERTICES];
    int via_visited[MAX_VERTICES];

    for (i = 0; i < G->num_vertices; i++) {
        dist[i] = INF;
        visited[i] = 0;
        prev[i] = -1;
        avoid_visited[i] = 0;
        via_visited[i] = 0;
    }

    dist[src] = 0;

    for (i = 0; i < G->num_vertices - 1; i++) {
        u = get_min_distance(dist, visited, G->num_vertices);
        visited[u] = 1;

        for (j = 0; j < G->num_vertices; j++) {
            if (!visited[j] && G->edges[u][j].weight != INF) {
                if (u == avoid || j == avoid)
                    avoid_visited[u] = avoid_visited[j] = 1;

                alt = dist[u] + G->edges[u][j].weight;

                if (alt < dist[j]) {
                    dist[j] = alt;
                    prev[j] = u;
                }
            }
        }
    }

    if (via >= 0 && !avoid_visited[via]) {
        printf("No path from %d to %d via %d\n", src, dest, via);
        return;
    }

    if (dist[dest] == INF) {
        printf("No path from %d to %d\n", src, dest);
        return;
    }

    printf("Shortest path from %d to %d:\n", src, dest);

    u = dest;
    while (u != -1) {
        printf("%d ", u);
        u = prev[u];
    }
    printf("\n");

    if (via >= 0 && !via_visited[via]) {
        printf("Path from %d to %d via %d:\n", src, dest, via);

        u = dest;
        while (u != -1) {
            printf("%d ", u);
            u = prev[u];

            if (u == via)
                via_visited[via] = 1;
        }

        u = via;
        while (u != -1) {
            printf("%d ", u);
            u = prev[u];

            if (u == -1 || via_visited[u])
                break;
        }

        printf("\n");
    }
}

int main()
{
    Graph G;
    int i, n, m, u, v, w, src, dest, avoid, via;

    printf("Enter the number of vertices: ");
    scanf("%d", &n);

    create_graph(&G, n);

    printf("Enter the number of edges: ");
    scanf("%d", &m);

    printf("Enter the edges (u v w):\n");
    for (i = 0; i < m; i++) {
        scanf("%d %d %d", &u, &v, &w);
        add_edge(&G, u, v, w);
    }

    printf("Enter the source vertex: ");
    scanf("%d", &src);

    printf("Enter the destination vertex: ");
    scanf("%d", &dest);

    printf("Enter the vertex to avoid (-1 for none): ");
    scanf("%d", &avoid);

    printf("Enter the vertex to visit (-1 for none): ");
    scanf("%d", &via);

    dijkstra(&G, src, dest, avoid, via);

    return 0;
}

其中，`create_graph`函数用于创建邻接矩阵表示的图，`add_edge`函数用于添加边，`get_min_distance`函数用于获取当前距离最小的未访问结点，`dijkstra`函数用于实现Dijkstra算法，其中通过`avoid`和`via`参数实现了题目所要求的避开指定点和必经指定点的功能。在`main`函数中，用户可以输入图的信息和所需求解的路径信息。