数据结构用C语言代码实现：建立顶点集为字符集的无向图的领接矩阵存储并输出，输入时的格式为“输入第一条边（vi，vj）和权值：a b 5””

#include <stdio.h>

#define MAX_VERTEX_NUM 20 //最大顶点数

typedef struct {
    char vertex[MAX_VERTEX_NUM]; //顶点集合
    int edge[MAX_VERTEX_NUM][MAX_VERTEX_NUM]; //邻接矩阵
    int vertexNum, edgeNum; //顶点数和边数
}Graph;

//初始化图
void initGraph(Graph *G) {
    int i, j;
    G->vertexNum = 0;
    G->edgeNum = 0;
    for (i = 0; i < MAX_VERTEX_NUM; i++) {
        G->vertex[i] = '\0';
        for (j = 0; j < MAX_VERTEX_NUM; j++) {
            G->edge[i][j] = 0;
        }
    }
}

//添加顶点
void addVertex(Graph *G, char v) {
    G->vertex[G->vertexNum++] = v;
}

//添加边
void addEdge(Graph *G, int vi, int vj, int w) {
    G->edge[vi][vj] = w;
    G->edge[vj][vi] = w; //无向图对称
    G->edgeNum++;
}

int main() {
    Graph G;
    initGraph(&G);

    int i, j, w;
    char v1, v2;
    printf("请输入边（vi，vj）和权值，输入-1 -1 -1结束：\n");
    while (scanf("%c %c %d", &v1, &v2, &w) == 3) {
        getchar(); //读取回车符
        if (v1 == '-' && v2 == '-' && w == -1) {
            break;
        }
        //判断顶点是否已存在
        for (i = 0; i < G.vertexNum; i++) {
            if (G.vertex[i] == v1) {
                break;
            }
        }
        if (i == G.vertexNum) {
            addVertex(&G, v1);
        }
        for (i = 0; i < G.vertexNum; i++) {
            if (G.vertex[i] == v2) {
                break;
            }
        }
        if (i == G.vertexNum) {
            addVertex(&G, v2);
        }
        //添加边
        for (i = 0; i < G.vertexNum; i++) {
            if (G.vertex[i] == v1) {
                break;
            }
        }
        for (j = 0; j < G.vertexNum; j++) {
            if (G.vertex[j] == v2) {
                break;
            }
        }
        addEdge(&G, i, j, w);
    }

    //输出邻接矩阵
    printf("邻接矩阵为：\n");
    printf("  ");
    for (i = 0; i < G.vertexNum; i++) {
        printf("%c ", G.vertex[i]);
    }
    printf("\n");
    for (i = 0; i < G.vertexNum; i++) {
        printf("%c ", G.vertex[i]);
        for (j = 0; j < G.vertexNum; j++) {
            printf("%d ", G.edge[i][j]);
        }
        printf("\n");
    }

    return 0;
}