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c++ - c++错误：指向数组的指针

问题描述

在 XCode 中它说：Thread 1: EXC_BAD_ACCESS (code=1, address=0x3c000003e7)

#include <stdio.h>
#include "Assistance.h"
#define infity 999

using namespace std;
class WeightedDirGraph
{
public:
    WeightedDirGraph();
    WeightedDirGraph(int **g, int size);
    ~WeightedDirGraph();
    void BellmanFord();
    void Display();
protected:
    int size;
    int (*(*graph));

};

WeightedDirGraph::WeightedDirGraph(int **g, int s)
{
    int a[s][s];
    graph=(int **)new int *[s];
    for(int i=0;i<s;++i)
    {
        for(int j=0;j<s;++j)
        {
            printf("%d ",*(*(g+i)+j));      //THIS IS THE LINE OF CODE THAT SEEMS TO BE WRONG
        }
        cout<<endl;
    }
    size=s;  
}



int main()
{

  char vexs[] = {'A', 'B', 'C', 'D', 'E', 'F', 'G', };
  int m[7][7] =
    {
      {infity,     60,     50,     50,  infity, infity,  infity},
      {infity, infity, infity, infity,     -10, infity,  infity},
      {infity,    -20, infity, infity,      10, infity,      70},
      {infity, infity,    -20, infity,  infity,    -10,  infity},
      {infity, infity, infity, infity,  infity, infity,      30},
      {infity, infity, infity, infity,  infity, infity,      30},
      {infity, infity, infity, infity,  infity, infity,  infity}
    };
    WeightedDirGraph *g=new WeightedDirGraph((int **)m,7);


}

我试图传递一个指向二维数组的指针并初始化这个 WeightedDirGraph。但我无法运行此代码。我认为当我使用指针时一定有某种错误，但我不知道问题是什么。有人能帮我吗？非常感谢。

标签： c++arrayspointersdata-structures

解决方案

数组不是指针，再多的转换也无法改变这一事实。
*(g+i)(ie g[i]) is m[i]，这是一个int[7]，而不是一个int*。
当您将其第一个元素解释为地址时，就会出现欢闹。

您需要从一个指针数组开始，因为它可以转换为指向指针的指针。

只需对代码进行少量更改，它可能如下所示：

int m[7][7] =
{
  {infity,     60,     50,     50,  infity, infity,  infity},
  {infity, infity, infity, infity,     -10, infity,  infity},
  {infity,    -20, infity, infity,      10, infity,      70},
  {infity, infity,    -20, infity,  infity,    -10,  infity},
  {infity, infity, infity, infity,  infity, infity,      30},
  {infity, infity, infity, infity,  infity, infity,      30},
  {infity, infity, infity, infity,  infity, infity,  infity}
};
int* mp[7] = {m[0], m[1], m[2], m[3], m[4], m[5], m[6]};
WeightedDirGraph *g=new WeightedDirGraph(mp, 7);

更好的解决方案可能是重新考虑您的实现并将数据存储在一维std::vector.
此外，g[i][j]比 . 更容易理解*(*(g+i)+j)。

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