簡單貪喫蛇遊戲的C++實現

我大概在一個多月前把自己上學期寫的c代碼的貪喫蛇遊戲push到csdn上，並且說c風格的貪喫蛇寫起來有些麻煩（貪喫蛇遊戲的c語言實現），準備用面向對象的c++再寫一遍。現在我們專業恰好剛教完了c++，學校也佈置了一道簡單的貪喫蛇的編程題目，實現下來，的確覺得c++的思路清晰很多，所以再次把c++的代碼push上來，供大家對比參考：）

直接上代碼，c++把整個遊戲拆分成幾個文件，分開上，有一定的c++基礎的同學應該可以很容易看懂。

1、全局頭文件(global.hpp)

#ifndef _GLOBAL_H_
#define _GLOBAL_H_

#ifndef SYMBOLS
#define HEAD '@'
#define BODY 'X'
#define EMPTY '+'
#define FOOD '$'
#endif  // !SYMBOLS

enum direction { up = 0, down = 1, left = 2, right = 4, freeze = 5 };

struct point {
  int x;
  int y;
  point(int x = 0, int y = 0) : x(x), y(y) {}
  point(const point& another) : x(another.x), y(another.y) {}
  point& operator=(const point& other) {
    x = other.x;
    y = other.y;
    return *this;
  }
  friend bool operator==(const point& point1, const point& point2) {
    return point1.x == point2.x && point1.y == point2.y;
  }
  point& move(direction d) {
    switch (d) {
      case up:
        x--;
        break;
      case down:
        x++;
        break;
      case left:
        y--;
        break;
      case right:
        y++;
        break;
      case freeze:
      default:
        break;
    }
    return *this;
  }
};

#endif  // !_GLOBAL_H_

2、snake類的聲明和實現(snake.hpp)

（爲了簡化結構，把聲明和實現共同放在了hpp文件裏，減少了一點封裝性，實際上應該分開頭文件和實現文件好一點）

此處使用了容器list作爲蛇身(body)的表達形式，這樣可以非常方便地進行表達，讀者有興趣可以用數組實現一下，一不小心就會出現有趣的內存錯誤。。。

#ifndef _SNAKE_H_
#define _SNAKE_H_
#include <iostream>
#include <list>
#include "global.hpp"

class snake {
        point head;
        std::list<point> body;
    public:
        snake(point initial_head);
        snake();
        ~snake() {}
        point& getHead();
        std::list<point>& getbody();
        void grow(point);
        void setHead(point);
};

snake::snake() {
    head.x = 0;
    head.y = 0;
}

snake::snake(point initial_head) {
    setHead(initial_head);
}

void snake::setHead(point _head) {
    head = _head;
}

void snake::grow(point second_node) {
    this -> body.push_front(second_node);
}

point& snake::getHead() {
    return head;
}

std::list<point>& snake::getbody() {
    return body;
}
#endif

3、map類的聲明和實現(map.hpp)

在這裏，map中應該包含一個snake類作爲組合關係。
在組合關係裏面，想要直接修改snake的各種參數是不可行的，所以在前面snake類的聲明裏加上了諸如setHead(), getHead(), getbody() 這一類的函數。

#ifndef _MAP_H_
#define _MAP_H_
#include <iostream>
#include "global.hpp"
#include "snake.hpp"

class map {
    private:
        char** _map;
        snake _snake;
        int height, width;
        std::list<point> foods;
    public:
        map();
        map(point initial_size, point initial_head,
        std::list<point> initial_foods);
        ~map();
        void move(direction d);
        void print();
        bool isGameOver();
        bool isEat();;
        void makemap(void);
};

map::map() {
    _map = NULL;
    height = width = 0;
}

void map::makemap() { // 這個是用來更新地圖的
    for (int i = 0; i < height; i++) {
        for (int j = 0; j < width; j++)
            _map[i][j] = 0;
    }
    for (std::list<point>::iterator i = foods.begin(); i != foods.end(); ++i) {
        _map[i->x][i->y] = FOOD;
    }
    _map[_snake.getHead().x][_snake.getHead().y] = HEAD;
    for (std::list<point>::iterator i = _snake.getbody().begin();
    i != _snake.getbody().end(); ++i) {
        _map[i->x][i->y] = BODY;
    }
    for (int i = 0; i < height; i++) {
        for (int j = 0; j < width;  j++) {
            if (_map[i][j] == 0)
                _map[i][j] = EMPTY;
        }
    }
}

map::map(point initial_size, point initial_head, std::list<point> initial_foods)
{
    height = initial_size.x;
    width = initial_size.y;
    _map = new char*[height];
    for (int i = 0; i < height; i++)
        _map[i] = new char[width]();
    _snake.setHead(initial_head);
    foods = initial_foods;
    makemap();
}

map::~map() {
    for (int i = 0; i < height; i++) {
        delete []_map[i];
    }
    delete []_map;
}

void map::print() {
    for (int i = 0; i < height; i++) {
        for (int j = 0; j < width; j++) {
            std::cout << _map[i][j];
        }
        std::cout << std::endl;        
    }
    std::cout << std::endl;
}

bool map::isGameOver() {
    point temp = _snake.getHead();
    if (temp.x == height || temp.y == width || temp.x < 0 || temp.y < 0)
        return true;
    if (_map[temp.x][temp.y] == BODY) return true;
    return false;
}

bool map::isEat() {
    point temp = _snake.getHead();
    if (temp.x == height || temp.y == width || temp.x < 0 || temp.y < 0)
        return false;
    if (_map[temp.x][temp.y] == FOOD) return true;
    else return false;
}

void map::move(direction d) {
    point temp_f = _snake.getHead();
    if (!(_snake.getbody().empty())) {  // 爲了避免追尾問題
        _map[_snake.getbody().back().x][_snake.getbody().back().y] = EMPTY;
    }
    _snake.getHead().move(d);
    if (_snake.getHead() == _snake.getbody().front()) {  // 判斷蛇是否往回走
        _snake.setHead(temp_f);
        _map[_snake.getbody().back().x][_snake.getbody().back().y] = BODY;
        return;
    }
    if (!isGameOver()) {
        if (isEat()) {
            point eaten = _snake.getHead();
            foods.remove(eaten);
            _snake.grow(temp_f);
        } else {
            _snake.getbody().push_front(temp_f);
            _snake.getbody().pop_back();
        }
        makemap();
    } else {
        if (!(_snake.getbody().empty())) {
            _map[_snake.getbody().back().x][_snake.getbody().back().y] = BODY;
        }
    }
}
#endif

蛇移動的算法是，頭先動，如果判斷可以走，則把頭原來的位置push_front到body的頭部，然後用pop_back把body的尾部抹去
（讀者不熟悉list容器的操作的話可以先去了解一下，很容易的：））

4、遊戲運行主文件(game.cpp)

#include "map.hpp"
#include "global.hpp"
#include <iostream>
#include <list>
#include <algorithm>

using std::cin;
using std::cout;
using std::cerr;
using std::endl;

class InvalidInputException {
 public:
  InvalidInputException() { cerr << "Invalid input!" << endl; }
};
class DuplicateInputException : public InvalidInputException {
 public:
  DuplicateInputException() { cerr << "Duplicate input!" << endl; }
};

class GameUI {
 private:
  map* world;
  point initial_size;
  point initial_head;
  std::list<point> initial_foods;

 public:
  GameUI() {
    cout << "please input two positive integers indicates the map size!"
         << endl;
    cin >> initial_size.x >> initial_size.y;
    if (initial_size.x <= 5 || initial_size.y <= 5 || initial_size.x > 15 ||
        initial_size.y > 15) {
      cout << "invalid input" << endl;
      throw InvalidInputException();
    }
    cout << "please input two positive integers(range(0, size_x-1), "
            "range(0,size_y-1)) the initialize snake head position!"
         << endl;
    cin >> initial_head.x >> initial_head.y;
    if (initial_head.x >= initial_size.x || initial_head.x < 0 ||
        initial_head.y >= initial_size.y || initial_head.y < 0) {
      cout << "invalid input" << endl;
      throw InvalidInputException();
    }
    int food_num;
    cout << "please input how many food you will put and then input food "
            "position which is different form each other"
         << endl;
    cin >> food_num;

    if (food_num <= 0) {
      throw InvalidInputException();
    }

    while (food_num > 0) {
      food_num--;
      point temp;
      cin >> temp.x >> temp.y;
      if (temp.x >= 0 && temp.x < initial_size.x && temp.y >= 0 &&
          temp.y < initial_size.y &&
          std::find(initial_foods.begin(), initial_foods.end(), temp) ==
              initial_foods.end() &&
          !(temp.x == initial_head.x && temp.y == initial_head.y)) {
        initial_foods.push_back(temp);
      } else {
        throw DuplicateInputException();
      }
    }

    world = new map(initial_size, initial_head, initial_foods);
  }

  ~GameUI() { delete world; }

  void GameLoop() {
    world->print();
    bool exit = false;
    while (true) {
      char operation = getInput();
      switch (operation) {
        case 'w':
        case 'W':
          this->world->move(up);
          break;
        case 's':
        case 'S':
          this->world->move(down);
          break;
        case 'a':
        case 'A':
          this->world->move(left);
          break;
        case 'd':
        case 'D':
          this->world->move(right);
          break;
        case 'q':
        case 'Q':
          exit = true;
          break;
        default:
          this->world->move(freeze);
      }
      world->print();
      if (world->isGameOver()) {
        cout << "Game Over!" << endl;
        break;
      }
      if (exit) {
        cout << "Bye!" << endl;
        break;
      }
    }
  }

  char getInput() {
    char temp;
    cin >> temp;
    return temp;
  }
};

int main() {  // 看，main函數只有這麼短！！！！
  GameUI greedySnake;
  greedySnake.GameLoop();
  return 0;
}

（事實上爲了達到封裝性，gameUI的類也應該分開來實現。）

5、小結

這個貪喫蛇還比較的低端，只能實現一鍵一步的行走方式，還沒有像我的c語言貪喫蛇那樣可以自己走，並且有AI模式。實現自己走要使用到windows的下的一個庫，實現起來還比較麻煩，可以參考我的c貪喫蛇。用c++重寫一遍貪喫蛇，主要作用是可以更加清楚地體會到類的封裝與使用。

以後如果有時間，筆者可能會爲這個貪喫蛇寫下補丁什麼的，體會一下c++的代碼重用和方便修改的特性，這是c語言所沒有的優點。

Enjoy coding! :)