1 December

Arrays as function parameters, 2-D arrays

#include <stdio.h>

/* Arrays as function parameters

Normally we pass single variables to functions.
  void f(int x);

Can also pass an array:
*/
  const int SIZE = 6;
  void f(int x[]){}  // size unspecified, ok
  void g(int x[SIZE]){} // size specified, ok
  void h(int x[10]){} // ok
  int main2() {
     int array[SIZE]; // create array
	 f(array);  // okay
     g(array);  // okay
	 h(array);  // size mismatch, but compiler doesn't care.
	 return 0;
  }
/* Passing array behaves differently than
   other parameters. It's more like call by
   reference.
   */
void ff(int x, int& y, int a[3])
{
	x = 4; 
	y = 5;
	a[0] = 6;
	a[1] = 7;
	a[2] = 8;
}

int main3()
{
	int c = 99;
	int d = 98;
	int a[3] = { 97, 96, 95 }; // array initialization
	printf("%d,%d,%d,%d,%d\n",c,d,a[0],a[1],a[2]);
	ff(c, d, a);
	printf("%d,%d,%d,%d,%d\n",c,d,a[0],a[1],a[2]);
	// The function ff CAN change the values
	// of the array, just like it can change
	// the reference parameter.
	return 0;
}


/* Two-dimensional arrays.

  So far, arrays have been one-dimensional.
     int a[5] = {0,1,2,3,4,5};
  Represented by one row of boxes.

  int b[5][3];  // 5 rows, 3 columns

  Diagram:
         0       1       2
    0  [0][0]  [0][1]  [0][2]
	1  [1][0]   etc.
	2
	3
    4

More dimensions possible, but rare.
Imagine 3 dimensions as a stack of paper,
with a 2-D grid on each sheet. Then,
a[3][5][2] would refer to sheet 3, row 5, column 2
*/

int main4()
{
	const int ROWS = 18;
	const int COLS = 8;
	int grid[ROWS][COLS];
	// Let's initialize it to a multiplication
	// table.
	for(int i = 0; i < ROWS; i++)
	{
		for(int j = 0; j < COLS; j++)
		{
			grid[i][j] = (i+1) * (j+1);
		}
	}
	// print out entire grid
	for(int i = 0; i < ROWS; i++)
	{
		for(int j = 0; j < COLS; j++)
		{
			printf("%5d ", grid[i][j]);
		}
		printf("\n");
	}
	return 0;
}

Help on assignment

See the experimentation in main. It’s your job to combine these function definitions and hints with the structure already given on the assignment page.

/* Output the grid onto the screen using printf. */
void output_grid (char grid[M][N])
{
	for(int i = 0; i < M; i++)
	{
		for(int j = 0; j < N; j++)
		{
			printf("%c", grid[i][j]);
		}
		printf("\n");
	}
}

// Fill grid with . character
void initialize_grid(char grid[M][N])
{
int j; int i;
	for (i = 0; i < M ; i++)
		{
		for (j = 0; j < N; j++)
			{
				grid [i] [j]= ('.');
			}
		}
}

int main()
{
    char grid[M][N];
    srand(time(NULL));
    initialize_grid(grid);
	// some experimentation
	int i = 2;
	int j = 3;
	char letter = 'A';
	grid[i][j] = letter;
	i++; // move down
	letter++; // next letter 
	grid[i][j] = letter;
	j++; // move right
	letter++; // next letter
	grid[i][j] = letter;
	// You'll need to loop thru letters.
	while(letter < 'Z')
	{
		letter++;
		printf("%c", letter);
	}
	printf("\n");
    // TODO
    output_grid(grid);
    return 0;
}