2048.c

// Original file by Jay Chan:
// https://gist.github.com/justecorruptio/9967738

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

#define SIDE 4
#define GRID (SIDE * SIDE)

int M[GRID];
int W;
int K[] = { 2, 3, 1, 0 };


int
cell (int d, int i, int j)
{
  if (d <= 0) {
    return SIDE * i + j;
  }

  return cell (d - 1, j, SIDE - 1 - i);
}

void
draw (int f, int d)
{
  int k, i = SIDE, j, l, P;

  for (; i--;) {
    j = k = l = 0;

    for (; k < SIDE;) {
      if (j < SIDE) {
        P = M[cell (d, i, j++)];
        W |= P >> 11;
        l *P && (f ? M[cell (d, i, k)] = l << (l == P) : 0, k++);
        l = l ? (P ? (l - P ? P : 0) : l) : P;
      }
      else {
        f ? M[cell (d, i, k)] = l : 0;
        ++k;
        W |= 2 * !l;
        l = 0;
      }
    }
  }
}

void
step ()
{
  int k, i = GRID + rand () & (GRID - 1);

  for (; M[i & (GRID - 1)] * i; i--);

  i ? M[i & (GRID - 1)] = 2 << (rand () % 2) : 0;
  W = i = 0;

  for (; i < SIDE; i++) {
    draw (0, i);
  }

  // print the tiles onto the terminal
  i = GRID;
  puts ("\e[2J\e[H");

  for (; i--;) {
    if (M[i]) {
      printf ("%4d|", M[i]);
    } else {
      printf ("%s", "    |");
    }

    if (0 == (i % SIDE)) {
      putchar ('\n');
    }
  }

  if (!(W - 2)) {
    // read input from keyboard
    read (0, &k, 3);
    draw (1, K[(k >> 16) & 3]);
    step ();
  }
}

int
main (void)
{
  // clear the screen in preparation for the game
  system ("stty cbreak");

  /* intialize random number generator */
  srand ((unsigned) time (NULL));

  step ();

  // game has finished by this point
  puts (W & 1 ? "Won" : "Lost");

  return 0;
}

//[2048]