snake_game.cpp

#include <iostream>
#include <vector>
#include <cstdlib>
#include <ctime>
#include <conio.h>
#include "windows.h"
using namespace std;


bool gameOver = false;
int score = 0;
const unsigned int gameSpeed = 200;  // ms per frame
const int SCREEN_WIDTH = 20;  // width in symbols
const int SCREEN_HEIGHT = 10;
const char WALL = '#';
const char FRUIT = 'F';
const char HEAD = 'O';
const char BODY = 'o';

/*
x is the row, y is the column:

     0 ----> X axis
     |
     |
     v
   Y axis
*/
int fruitX, fruitY;
int headX, headY;
vector<COORD> tail;
enum class Dir { STOP, LEFT, RIGHT, UP, DOWN };
Dir dir;  // the current heading of head

void setCursorPosition(int x, int y) {
  // x is the column, y is the row. The origin (0,0) is top-left.
  static const HANDLE hOut = GetStdHandle(STD_OUTPUT_HANDLE);
  std::cout.flush();
  COORD coord = {(SHORT)x, (SHORT)y};
  SetConsoleCursorPosition(hOut, coord);
}

void Setup() {
  fruitX = rand() % (SCREEN_HEIGHT - 2) + 1;
  fruitY = rand() % (SCREEN_WIDTH - 2) + 1;

  do {
    headX = rand() % (SCREEN_HEIGHT - 2) + 1;  // SCREEN_HEIGHT / 2;
    headY = rand() % (SCREEN_WIDTH - 2) + 1;   // SCREEN_WIDTH / 2;
  } while (headX == fruitX && headY == fruitY);
}

void Draw() {
  system("cls");

  for (size_t j = 0; j < SCREEN_WIDTH; j++) cout << WALL;
  cout << endl;

  for (size_t i = 1; i < SCREEN_HEIGHT - 1; i++) {
    for (size_t j = 0; j < SCREEN_WIDTH; j++) {
      if (j == 0 || j == SCREEN_WIDTH - 1)
        cout << WALL;
      else if (headX == i && headY == j)
        cout << HEAD;
      else if (fruitX == i && fruitY == j)
        cout << FRUIT;
      else {
        bool print = false;
        for (auto t : tail) {
          if (t.X == i && t.Y == j) {
            cout << BODY;
            print = true;
          }
        }
        if (!print) cout << ' ';
      }
    }
    cout << endl;
  }

  for (size_t j = 0; j < SCREEN_WIDTH; j++) cout << WALL;
  cout << endl << "Score: " << score << endl;
}

void Input() {
  if (_kbhit()) {
    switch (_getch()) {
      case 'a': case 'A':
        if (dir == Dir::RIGHT) dir = Dir::STOP;
        else dir = Dir::LEFT;
        break;
      case 'd': case 'D':
        if (dir == Dir::LEFT) dir = Dir::STOP;
        else dir = Dir::RIGHT;
        break;
      case 'w': case 'W':
        if (dir == Dir::DOWN) dir = Dir::STOP;
        else dir = Dir::UP;
        break;
      case 's': case 'S':
        if (dir == Dir::UP) dir = Dir::STOP;
        else dir = Dir::DOWN;
        break;
      case 'x': case 'X':
        gameOver = true;
        break;
      default: break;
    }
  }
}

void Logic() {

  // move tail pos
  if (tail.size() && dir != Dir::STOP) {
    short prevX = tail[0].X;
    short prevY = tail[0].Y;
    short prev2X, prev2Y;

    tail[0].X = headX;
    tail[0].Y = headY;

    for (size_t i = 1; i < tail.size(); i++) {
      prev2X = tail[i].X;
      prev2Y = tail[i].Y;
      tail[i].X = prevX;
      tail[i].Y = prevY;
      prevX = prev2X;
      prevY = prev2Y;
    }
  }
  
  // move head pos
  switch (dir) {
    case Dir::LEFT:
      headY--;
      break;
    case Dir::RIGHT:
      headY++;
      break;
    case Dir::UP:
      headX--;
      break;
    case Dir::DOWN:
      headX++;
      break;
    case Dir::STOP:
      break;
  }

  // check collisions
  for (auto t : tail) {
    if (headX == t.X && headY == t.Y) gameOver = true;
  }
  if (headX == fruitX && headY == fruitY) {
    score++;
    fruitX = rand() % (SCREEN_HEIGHT - 2) + 1;
    fruitY = rand() % (SCREEN_WIDTH - 2) + 1;
    COORD newTailEl{headX, headY};
    tail.push_back(newTailEl);
  } else if (headX == 0 || headX == SCREEN_HEIGHT - 1 || headY == 0 ||
      headY == SCREEN_WIDTH - 1) {
    gameOver = true;
  }
}

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

  Setup();
  while (!gameOver) {
    Draw();
    Input();
    Logic();
    Sleep(gameSpeed);
  }

  cout << "\nGame over\n";
  system("pause");
  return 0;
}