简单贪吃蛇游戏的C++实现

1全局头文件globalhpp

2snake类的声明和实现snakehpp

3map类的声明和实现maphpp

4游戏运行主文件gamecpp

5小结

我大概在一个多月前把自己上学期写的c代码的贪吃蛇游戏push到csdn上，并且说c风格的贪吃蛇写起来有些麻烦（贪吃蛇游戏的c语言实现），准备用面向对象的c++再写一遍。现在我们专业恰好刚教完了c++，学校也布置了一道简单的贪吃蛇的编程题目，实现下来，的确觉得c++的思路清晰很多，所以再次把c++的代码push上来，供大家对比参考：）

直接上代码，c++把整个游戏拆分成几个文件，分开上，有一定的c++基础的同学应该可以很容易看懂。

1、全局头文件(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类的声明和实现(snake.hpp)

（为了简化结构，把声明和实现共同放在了hpp文件里，减少了一点封装性，实际上应该分开头文件和实现文件好一点）

此处使用了容器list作为蛇身(body)的表达形式，这样可以非常方便地进行表达，读者有兴趣可以用数组实现一下，一不小心就会出现有趣的内存错误。。。

#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类的声明和实现(map.hpp)

在这里，map中应该包含一个snake类作为组合关系。

在组合关系里面，想要直接修改snake的各种参数是不可行的，所以在前面snake类的声明里加上了诸如setHead(), getHead(), getbody() 这一类的函数。

#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() { // 这个是用来更新地图的
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())) {  // 为了避免追尾问题
_map[_snake.getbody().back().x][_snake.getbody().back().y] = EMPTY;
}
_snake.getHead().move(d);
if (_snake.getHead() == _snake.getbody().front()) {  // 判断蛇是否往回走
_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

蛇移动的算法是，头先动，如果判断可以走，则把头原来的位置push_front到body的头部，然后用pop_back把body的尾部抹去

（读者不熟悉list容器的操作的话可以先去了解一下，很容易的：））

4、游戏运行主文件(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函数只有这么短！！！！
GameUI greedySnake;
greedySnake.GameLoop();
return 0;
}

（事实上为了达到封装性，gameUI的类也应该分开来实现。）

5、小结

这个贪吃蛇还比较的低端，只能实现一键一步的行走方式，还没有像我的c语言贪吃蛇那样可以自己走，并且有AI模式。实现自己走要使用到windows的下的一个库，实现起来还比较麻烦，可以参考我的c贪吃蛇。用c++重写一遍贪吃蛇，主要作用是可以更加清楚地体会到类的封装与使用。

以后如果有时间，笔者可能会为这个贪吃蛇写下补丁什么的，体会一下c++的代码重用和方便修改的特性，这是c语言所没有的优点。

Enjoy coding! :)