環(huán)境：VS2017

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

#define OK 1
#define ERROR 0
#define TRUE 1
#define FALSE 0
#define MAXVEX 100  //最大頂點(diǎn)數(shù)，用戶自定義
#define INFINITY 65535

typedef int Status;
typedef char VertexType;
typedef int EdgeType;

typedef struct
{
    VertexType vexs[MAXVEX];    //頂點(diǎn)表
    EdgeType arc[MAXVEX][MAXVEX];   //邊表
    int numNodes, numEdges; //圖中當(dāng)前的頂點(diǎn)和邊表
}MGraph;

//建立無向網(wǎng)圖的鄰接矩陣
void CreateMGraph(MGraph *G)
{
    int i, j, k, w;
    printf("輸入頂點(diǎn)數(shù)和邊數(shù):\n");
    scanf_s("%d%d", &G->numNodes, &G->numEdges);    //輸入頂點(diǎn)數(shù)和邊數(shù)
    for (i = 0; i < G->numNodes; i++)
        scanf_s(&G->vexs[i]);

    for (i = 0; i < G->numNodes; i++)   //初始化
        for (j = 0; j < G->numNodes; j++)
            G->arc[i][j] = INFINITY;

    for (k = 0; k < G->numEdges; k++)
    {
        printf("輸入邊(vi,vj)上的下標(biāo)i，下標(biāo)j和權(quán)w:\n");
        scanf_s("%d%d%d", &i, &j, &w);
        G->arc[i][j] = w;
        G->arc[j][i] = G->arc[i][j];    //無向圖，矩陣對稱
    }

    for (i = 0; i < G->numNodes; i++)
    {
        for (j = 0; j < G->numNodes; j++)
        {
            printf("%d\t",G->arc[i][j]);
        }
        printf("\n");
    }
}

int main()
{
    MGraph G;
    CreateMGraph(&G);

    system("pause");
    return 0;
}

測試如下：
輸入頂點(diǎn)數(shù)和邊數(shù):
3 3
輸入邊(vi,vj)上的下標(biāo)i，下標(biāo)j和權(quán)w:
0 0 1
輸入邊(vi,vj)上的下標(biāo)i，下標(biāo)j和權(quán)w:
1 1 3
輸入邊(vi,vj)上的下標(biāo)i，下標(biāo)j和權(quán)w:
1 2 5
1 65535 65535
65535 3 5
65535 5 65535