grid.c

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

typedef struct Cell {
    int by;
} Cell;

int main(int argc, char *argv[]) {
    int row = 5;
    int num_cells = row * row;
    Cell cells[num_cells];

    // Generate the game map
    int i = 0;
    unsigned int seed = (unsigned int)time(NULL);
    srandom(seed);
    for (i = 0; i < num_cells; i++) {
        int by = random() % 2;
        Cell this = {.by = by};
        cells[i] = this;

        printf("[%d] ", this.by);
        if ((i + 1) % 5 == 0) printf("\n");
    }

    printf("\n");

    // Check for defended cells
    for (i = 0; i < num_cells; i++) {
        Cell this = cells[i];

        char match = '\0';
        match |= (i - row < 0 || cells[i - row].by == this.by) << 3;
        match |= (i % row == row - 1 || cells[i + 1].by == this.by) << 2;
        match |= (i + row > num_cells - 1 || cells[i + row].by == this.by) << 1;
        match |= (i % row == 0 || cells[i - 1].by == this.by);

        char display = match == 15 ? 'D' : ' ';
        printf("[%c] ", display);
        if ((i + 1) % 5 == 0) printf("\n");
    }

    return 0;
}