动态二维数组实现 C

“定义一个二维指针的空间分配和释放 int **ptr”

1. 调用malloc 函数 次数： ( rows + 1)

 
int** New2DPointer(int m, int n)
{
if (m > 0 && n > 0)
{
typedef int * INT_POINTER;
int **ptr = NULL;
try {
ptr = new INT_POINTER[m];
for (int i = 0; i != m; ++i)
{
ptr[i] = new int[n];
}
}
catch (bad_alloc e)
{

std::cout << “Error allocating memory.” << std::endl;
}

return ptr;
}
else
{
std::cout << “invalided input parameters\n”;
}
}

void Delete2DPointer(int **p, int m)
{
for (int i = 0; i != m; ++i)
{
delete [] (p[m]);
}
}

调用malloc 函数 次数： ( 1 + 1)

int **array2d_new(size_t rows, size_t cols)
{
int **array2d, **end, **cur;
int *array;
cur = array2d = malloc(rows * sizeof(int *));
if (!array2d)
return NULL;

array = malloc(rows * cols * sizeof(int));
if (!array)
{
free(array2d);
return NULL;
}

end = array2d + rows;
while (cur != end)
{
*cur = array;
array += cols;
cur++;
}

//print_2d_array(m, rows, cols);
return array2d;
}

调用malloc 函数次数： ( 1 + 1)， 看上去更牛B些

void ** array2d(size_t rows, size_t cols, size_t value_size)
{
size_t index_size = sizeof(void *) * rows;
size_t store_size = value_size * rows * cols;

char * a = (char*)malloc(index_size + store_size);
if(!a) return NULL;

memset(a + index_size, 0, store_size);
for(size_t i = 0; i < rows; ++i)
((void **)a)[i] = a + index_size + i * cols * value_size;

return (void **)a;
}

int printf(const char *, ...);

int main()
{
int ** a = (int **)array2d(5, 5, sizeof(int));
assert(a);

for (int i = 0; i < 5; i++)
for (int j = 0; j < 5; j++)
a[i][j] = i*j;
//a[4][3] = 42;
for (int i = 0; i < 5; i++)
{
for (int j = 0; j < 5; j++)
printf("%i\t", a[i][j]);
printf("\n");
}

free(a);
return 0;
}

参考：
1. http://stackoverflow.com/questions/455960/dynamic-allocating-array-of-arrays-in-c
2. http://c-faq.com/aryptr/dynmuldimary.html