2048/main.c

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

#define BOARD_WIDTH 4
#define BOARD_HEIGHT 4
#define STARTING_TILES 3

typedef enum { UP = 0, DOWN, LEFT, RIGHT } MOVE_DIRECTION;
static int board[BOARD_HEIGHT][BOARD_WIDTH] = {0};

void print_board() {
  for (int y = 0; y < BOARD_HEIGHT; y++) {
    for (int x = 0; x < BOARD_WIDTH; x++) {
      printf("%d ", board[y][x]);
    }
    printf("\n");
  }
}

// Depending on the direction, move the tiles and check if we can merge with the
// tiles in that direction. We merge the tiles only if they are of the same value
// TODO: Add a guard agains double merge!
// 2 2 0 4 => 8 0 0 0 which is incorrect and should be 4 4 0 0
void move(MOVE_DIRECTION direction) {
  switch (direction) {
  case UP: {
    for (int y = 1; y < BOARD_HEIGHT; y++) {
      for (int x = 0; x < BOARD_WIDTH; x++) {
        if (board[y][x] == 0)
          continue;

        // Hard keeping track of this so I'm commenting as much as I can
        // Check if we can move up any space, so loop until we find a non-empty tile or the top of the board

        // py is the potential target y that we will settle for and move the tile into
        int target_y = y;
        for (int py = y - 1; py >= 0; py--) { // Go from the tile's current position up to the top of the board
          if (board[py][x] == 0) {
            target_y = py;
          } else if (board[py][x] == board[y][x]) {
            target_y = py;
            break;
          } else {
            break;
          }
        }

        // Check if we are moving anything
        if (target_y == y)
          continue;

        // If the target tile is empty, move the current tile there
        // If the target tile has the same value, merge them
        if (board[target_y][x] == 0) {
          board[target_y][x] = board[y][x];
          board[y][x] = 0;
        } else if (board[target_y][x] == board[y][x]) {
          board[target_y][x] *= 2;
          board[y][x] = 0;
        }
      }
    }
    break;
  }
  case DOWN: {
    for (int y = BOARD_HEIGHT - 1; y >= 0; y--) {
      for (int x = 0; x < BOARD_WIDTH; x++) {
        if (board[y][x] == 0)
          continue;

        int target_y = y;
        for (int py = y + 1; py < BOARD_HEIGHT; py++) {
          if (board[py][x] == 0) {
            target_y = py;
          } else if (board[py][x] == board[y][x]) {
            target_y = py;
            break;
          } else {
            break;
          }
        }

        if (target_y == y)
          continue;

        if (board[target_y][x] == 0) {
          board[target_y][x] = board[y][x];
          board[y][x] = 0;
        } else if (board[target_y][x] == board[y][x]) {
          board[target_y][x] *= 2;
          board[y][x] = 0;
        }
      }
    }
    break;
  }
  case LEFT: {
    for (int y = 0; y < BOARD_HEIGHT; y++) {
      for (int x = 1; x < BOARD_WIDTH; x++) {
        if (board[y][x] == 0)
          continue;

        int target_x = x;
        for (int px = x - 1; px >= 0; px--) {
          if (board[y][px] == 0) {
            target_x = px;
          } else if (board[y][px] == board[y][x]) {
            target_x = px;
            break;
          } else {
            break;
          }
        }

        if (target_x == x)
          continue;

        if (board[y][target_x] == 0) {
          board[y][target_x] = board[y][x];
          board[y][x] = 0;
        } else if (board[y][target_x] == board[y][x]) {
          board[y][target_x] *= 2;
          board[y][x] = 0;
        }
      }
    }
    break;
  }
  case RIGHT: {
    for (int y = 0; y < BOARD_HEIGHT; y++) {
      for (int x = BOARD_WIDTH - 1; x >= 0; x--) {
        if (board[y][x] == 0)
          continue;

        int target_x = x;
        for (int px = x + 1; px < BOARD_WIDTH; px++) {
          if (board[y][px] == 0) {
            target_x = px;
          } else if (board[y][px] == board[y][x]) {
            target_x = px;
            break;
          } else {
            break;
          }
        }

        if (target_x == x)
          continue;

        if (board[y][target_x] == 0) {
          board[y][target_x] = board[y][x];
          board[y][x] = 0;
        } else if (board[y][target_x] == board[y][x]) {
          board[y][target_x] *= 2;
          board[y][x] = 0;
        }
      }
    }
    break;
  }
  }
}

bool spawn_tile() {
  int empty_tiles[BOARD_WIDTH * BOARD_HEIGHT][2];
  int empty_count = 0;

  for (int y = 0; y < BOARD_HEIGHT; y++) {
    for (int x = 0; x < BOARD_WIDTH; x++) {
      if (board[y][x] == 0) {
        empty_tiles[empty_count][0] = y;
        empty_tiles[empty_count][1] = x;
        empty_count++;
      }
    }
  }

  if (empty_count == 0)
    return false;

  int random_index = rand() % empty_count;
  int spawn_y = empty_tiles[random_index][0];
  int spawn_x = empty_tiles[random_index][1];
  board[spawn_y][spawn_x] = (rand() % 10 == 0) ? 4 : 2; // 10% chance to spawn a 4

  return true;
}

int main() {
  srand(time(NULL));

  int tile_count = 0;
  while (tile_count != STARTING_TILES) {
    int y = rand() % BOARD_HEIGHT;
    int x = rand() % BOARD_WIDTH;

    if (board[y][x] != 0)
      continue;
    board[y][x] = (rand() % 10 == 0) ? 4 : 2; // 10% chance to spawn a 4
    tile_count++;
  }

  printf("2048 machen\n");
  print_board();
  move(UP);
  printf("After move up:\n");
  print_board();
  printf("After spawning a tile:\n");
  spawn_tile();
  print_board();
  move(DOWN);
  printf("After move down:\n");
  print_board();
  spawn_tile();
  printf("After spawning a tile:\n");
  print_board();
  move(LEFT);
  printf("After move left:\n");
  print_board();
  spawn_tile();
  printf("After spawning a tile:\n");
  print_board();
  move(RIGHT);
  printf("After move right:\n");
  print_board();
  return 0;
}