ISO 4683-1's stats

// example invocation: entry(g,5,5,5,2)
void entry(char *grid, size_t width, size_t height, size_t x, size_t y){
    size_t abs = (y-1)*width+x-1;
    size_t tot = width*height;
    for(int i=abs;!grid[i]&&i>0;i-=width){
        for(int j=i;!grid[j]&&j>=i-x+1;j--)
            grid[j]=1;
        for(int j=i+1;!grid[j]&&j<=i+width-x;j++)
            grid[j]=1;
    }
    if(!grid[abs])
        for(int i=abs+width;i<tot&&!grid[i];i+=width){
            for(int j=i;!grid[j]&&j>=i-x;j--)
                grid[j]=1;
            for(int j=i+1;!grid[j]&&j<=i+width-x;j++)
                grid[j]=1;
        }
}