Thread: Feeding a 2d array into a function

Hello,

I am trying to get a function to perform a task on a 2d array, the array itself is already created outside of the function and merely needs to be passed to it so that it can perfom an action on it.

For refrence the 2d array is a map (which can be created in different sizes) which has rooms in it. The function needs to perform an algorithm to connect corridors. I have been able to do this already but I now need to transfere it into a function.

Thanks in advance

you could receive it as simply a **array, with the dimensions passed as well.

Something like:

Code:

int draw_map( char **map, unsigned int width, unsigned int height )
{
// drawing code here
}

You'll have bounds checking available if you have the dimensions.

an alternative way that will compile without warnings and won't segfault is to pass the data in as if it were a 1D array, then compute the 2D index yourself.

Code:

void f(char *p,int rows,int cols) {
      int index;

      // index into 2D array
      // where the array is p[rows][cols]
      // index = (row * cols) + col

      // p[0][0]
      index  = 0 * cols + 0;
      // p[1][0]
      index = 1 * cols + 0;
      // p[0][1]
      index = 0 * cols + 1;
      // p[2][1]
      index = 2 * cols + 1
}

...
char *a[10][[10];
f(a[0],10,10);

But if I do this and feed in the array will it change the array I feed in, or do I have to return it and set the out of function array to equal the array returned by the function.

This is what I have done so far:

Code:

void zeroSight(int **sight, unsigned int rows, unsigned int columns){

    for(int i=0; i<columns; i++){ //initialise for loop to set seen to 0. This line go along y
    
        for(int j=0; j<rows; j++){ //on each y co-ordinate go along the x
        
            sight[j][i] = 1; //for each co-ordinate x and y set the seen value to 0 [or 1 to reveal map]
            
        }    
    }          
}

When I call the function in the main method:

Code:

zeroSight(mapSight, mapX, mapY );

I get the error
"cannot convert `int (*)[((unsigned int)((int)mapY))]' to `int**' for argument `1' to `void zeroSight(int**, int, int)' "

Any idea what I am doing wrong?

Thanks

another way:

Code:

#include <stdio.h>
#include <stdlib.h>


typedef char X[3][3];

void f(X x) {
        printf("%d\n",x[1][2]);
}

int main(int argc, char** argv)
{
        X x;
        x[1][2] = 3;
        f(x);

  return 0;
}