multidimensional array

[allomeen]

Hi, I having this error and i don't know how to fix it, can anybody help please:
"declaration of `c' as multidimensional array must have bounds for all dimensions except the first", i'm getting this error because of :

void lcs::LCS_Length(int X[], int Y[], int c[][], char b[][],  int m, int n)
{
	for( int i = 1; i < m; i++)
		c[i][0] = 0;
	for( int j = 1; j < n; j++)
		c[0][j] = 0;
	for( int i = 1; i < m; i++)
		for( int j = 1; j < n; j++)
		{
			if( X[i] == Y[j])
			{
				c[i][j] = c[i - 1][j - 1] + 1;
				b[i][j] = 'D';
			}

			else if(c[i - 1][j] >= c[i][j - 1])
			{
				c[i][j] = c[i - 1][j];
				b[i][j] = 'U';
			}
			else
			{
				c[i][j] = c[i][j - 1];
				b[i][j] = 'L';
			}
		}
}

<< moderator edit: added [code][/code] tags >>

[Dave Sinkula]

I find the diagnostic message quite self-explanitory.declaration of `c' as multidimensional array must have bounds for all dimensions except the firstYou can't do[][]. You can do [][5], for example.

[Dogtree]

You can omit the array size for the first dimension because array names are almost always converted to a pointer to the first element, so any size information is lost. That feature only applies to the first dimension, so you have to provide size information for the second dimension because the conversion to a pointer makes it a pointer to an array of N. These two function declarations are equivalent:

void foo(int a[][10]);
void bar(int (*a)[10]);

To avoid those errors, you can always provide sizes for all dimensions until you're comfortable with the rules. However, for arbitrary sizes in all dimensions, you have no choice but to use a dynamic array:

void foo(int **a, int m, int n);

int main()
{
  int **a = new int*[5];

  for (int i = 0; i < 5; i++)
    a[i] = new int[5];

  foo(a, 5, 5);

  for (int i = 0; i < 5; i++)
    delete [] a[i];
  delete [] a;
}

Of course, that's assuming you don't have libraries to work with. The standard vector class is well suited to this:

#include <vector>

void foo(std::vector<std::vector<int> > a);

The boost library also supports a multi_array class.