### 二维数组和二维指针

二维数组和二级指针，这真是头疼的问题，困扰了我好几次，

先转一下 wanpengcoder 的二维数组和二级指针

Fun (int **p){}这里面的int **p //这里的p不是二维数组的指针，而是指向指针的指针，即二级指针。

int **p=(int**)a;//强制将二维数组指针转为指向指针的指针

p[0][1]=*(*(p+0)+1)；

a是指向整个数组的首地址,并不是int **;所以不要指望向函数fun里面传实参 p=a;

#include <iostream>

void fun(char ** p)

{

char (*p1)[10] = (char(*)[10])p;

std::cout<<p1[0][0]<<std::endl;

}

int main(int argc, char* argv[])

{

char data[][10] = {"abc","def"};

fun((char **)data);

return 0;

}

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<c程序设计语言>中的关于这个的解释：

Newcomers to C are sometimes confused about the difference between a two-dimensional array and an array of pointers, such as name in the example above. Given the definitions

int a[10][20];

int *b[10];

then a[3][4] and b[3][4] are both syntactically legal references to a single int. But a is a true two-dimensional array: 200 int-sized locations have been set aside, and the conventional rectangular subscript calculation 20 * row +col is used to find the element a[row,col]. For b, however, the definition only allocates 10 pointers and does not initialize them; initialization must be done explicitly, either statically or with code. Assuming that each element of b does point to a twenty-element array, then there will be 200 ints set aside, plus ten cells for the pointers. The important advantage of the pointer array is that the rows of the array may be of different lengths. That is, each element of b need not point to a twenty-element vector; some may point to two elements, some to fifty, and some to none at all.

Although we have phrased this discussion in terms of integers, by far the most frequent use of arrays of pointers is to store character strings of diverse lengths, as in the function month_name. Compare the declaration and picture for an array of pointers:

char *name[] = { "Illegal month", "Jan", "Feb", "Mar" };￼

with those for a two-dimensional array:

char aname[][15] = { "Illegal month", "Jan", "Feb", "Mar" };