图的邻接矩阵

Question

我正在编写一个代码来实现图形的邻接矩阵。但是我遇到了运行时错误。谁能指出我错在哪里？

代码：

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

struct Graph{
    int V;
    int E;
    int **Adj;
};

void test(struct Graph *graph)
{
    graph->E = 5;
    graph->V = 4;
    graph->Adj = malloc(sizeof(graph->V * graph->V));
    graph->Adj[0][0] = 9;
    graph->Adj[0][1] = 7;
    graph->Adj[0][2] = 2;
    graph->Adj[0][3] = 5;
    printf("Hello %d\n",graph->Adj[0][2]);    
}
int main()
{
    struct Graph *graph = malloc(sizeof(struct Graph));
    test(graph); 
}

如果我在主函数中做同样的事情，它会起作用。我不明白我在编写测试函数时做错了什么？

在主函数中完成时的代码：

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

struct Graph{
    int V;
    int E;
    int **Adj;
};


int main()
{
    struct Graph *graph = malloc(sizeof(struct Graph));
    graph->E = 5;
    graph->V = 4;
    graph->Adj = malloc(sizeof(graph->V * graph->V));
    graph->Adj[0][0] = 9;
    graph->Adj[0][1] = 7;
    graph->Adj[0][2] = 2;
    graph->Adj[0][3] = 5;
    printf("Hello %d\n",graph->Adj[0][2]);

}

出现运行时错误。在调试 test function 时，它一直工作到 graph->Adj = malloc(sizeof(graph->V * graph->V));，但在 graph->Adj[0][0] = 9; 时出现错误。为什么？？？

Answer 1

你做错了 malloc。您正在使用指向指针的指针。因此，您必须先 malloc 才能动态分配数组指针。然后你必须为每一行分配它。

试试这个：

 graph->Adj = (int **)malloc(graph->v * sizeof(int *));
    for (i=0; i<graph->v; i++)
         graph->Adj[i] = (int *)malloc(graph->v * sizeof(int));