[英]c++ error : pointer that points to an array
In XCode it says:Thread 1: EXC_BAD_ACCESS (code=1, address=0x3c000003e7)在 XCode 中它说:线程 1:EXC_BAD_ACCESS(代码=1,地址=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);
}
I am trying to pass a pointer that points to a two dimensional array and initialize this WeightedDirGraph.我试图传递一个指向二维数组的指针并初始化这个 WeightedDirGraph。 But I can't run this code.
但我无法运行此代码。 I think there must be some sort of mistake when I am using the pointer, but I don't know what the problem is.
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。 Can someone help me?
有人能帮我吗? Thanks a lot.
非常感谢。
An array is not a pointer, and no amount of casting can change that fact.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]
, which is an int[7]
, not an int*
. *(g+i)
(即g[i]
)是m[i]
,它是int[7]
,而不是int*
。
When you interpret its first elements as an address, hilarity ensues.当您将其第一个元素解释为地址时,就会出现欢闹。
You need to start with an array of pointers, since that can be converted to a pointer to a pointer.您需要从指针数组开始,因为它可以转换为指向指针的指针。
With minimal changes to your code, it might look like this: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);
The better solution is probably to rethink your implementation and store the data in a one-dimensional std::vector
.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
中。
Also, g[i][j]
is much easier to follow than *(*(g+i)+j)
.此外,
g[i][j]
比*(*(g+i)+j)
更容易理解。
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