#include <stdio.h>

/* Applies the rules of Life to the grid. */
void updateGrid();
/* Prints out a representation of the grid using binary digits. */
void printGrid();

#define GRID_SIZE  10
#define ITERATIONS 10

/*  Conway's Game of Life as a C exercise.

    TODO: Allow command line arguments specifying the grid size and number of iterations.
*/

int main(int argc, char **argv)
{
    int grid[GRID_SIZE][GRID_SIZE] = {
        {0, 1, 0, 0, 0, 0, 0, 0, 0, 0},
        {0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
        {1, 0, 1, 0, 0, 0, 0, 0, 0, 0},
        {0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
        {0, 0, 0, 1, 1, 1, 0, 1, 0, 0},
        {0, 1, 0, 1, 0, 0, 0, 0, 1, 0},
        {0, 0, 0, 0, 0, 1, 1, 0, 0, 0},
        {0, 0, 0, 0, 1, 0, 0, 1, 0, 0},
        {1, 0, 0, 0, 0, 0, 0, 0, 0, 0},
        {0, 0, 1, 1, 1, 0, 1, 1, 1, 0}
    };

    printGrid(grid);
    printf("---\n");

    int i = 0;
    while (i < ITERATIONS)
    {
        updateGrid(&grid);
        i++;
    }

    printGrid(grid);
    return 0;
}

void updateGrid(int gridn[][GRID_SIZE])
{
    int i = 1, j = 1, n = 0;
    int alive = 0;
    int grid[GRID_SIZE][GRID_SIZE];
    memcpy(grid, gridn, sizeof(int) * GRID_SIZE * GRID_SIZE);

    while (i < GRID_SIZE)
    {
        while (j < GRID_SIZE)
        {
            if (grid[i-1][j-1] == 1) n++;
            if (grid[i-1][j]   == 1) n++;
            if (grid[i-1][j+1] == 1) n++;
            if (grid[i][j-1]   == 1) n++;
            if (grid[i][j]     == 1) alive = 1;
            if (grid[i][j+1]   == 1) n++;
            if (grid[i+1][j-1] == 1) n++;
            if (grid[i+1][j]   == 1) n++;
            if (grid[i+1][j+1] == 1) n++;

            // n is now the number of live neighbours of the current cell.
            if (!alive && n == 3)
            {   // Reproduce!
                gridn[i][j] = 1;
            }
            else if (alive && n != 2 && n != 3)
            {   // Overcrowding or no opportunity for reproduction. :<
                gridn[i][j] = 0;
            }

            n = 0;
            alive = 0;
            j++;
        }

        j = 1;
        i++;
    }
}

void printGrid(int grid[][GRID_SIZE])
{
    int i = 0, j = 0;

    while (i < GRID_SIZE)
    {
        while (j < GRID_SIZE)
        {
            printf("%d", grid[i][j]);
            j++;
        }

        printf("\n");
        j = 0;
        i++;
    }
}