高效率的贪吃蛇-Java实现

1.原因

前面写过一篇有关贪吃蛇实现的小文《 完全用链表实现的贪吃蛇》，其实现得很统一，几乎完全用链表实现了所有的元素，然而其效率不甚高。该实现虽然津津乐道于没有使用二维数组，然而却大量使用链表，实际上是将二维数组的双for循环换成了大量链表的遍历，虽然由于受到游戏面板长度宽度的限制，算法时间复杂度不会到O(N)，但效率仍不敢恭维。
经由验证考研，网上朋友的指点，加之自己的思考，今天重新实现了一版，去除了上一版的“抽象但无用”的“统一于链表”的思想，更多的融入了OO的思想以及一些优化，通篇没有一次遍历整个链表。

2.保留的链表以及更改的数据结构

虽然这一版声明不再使用链表，然而做事不能太极端，我还是保留了freelist链表，因为这在生成食物以及随机障碍物的时候十分有用，否则就要通过下面的算法进行了：
do { 随机生成一个位置 }while (该位置和蛇体冲突);
在长蛇阵的情况下，循环次数将增加。另外保留了deltalist，该链表指示了“哪些位置需要重画”，具体怎么重画和该位置的type属性有关，这就需要更改数据结构。该版贪吃蛇对数据结构进行了大量的封装，访问数据必须通过get/set方法进行，对position类进行了扩充，增加了type位属性，对snake进行了整体封装，不再将蛇链表导入Game_pad中，对于蛇的移动，取消了拐点链表，而是直接将蛇尾删除加入蛇头。

3.代码

import java.awt.*; import java.awt.event.*; import javax.swing.*; import java.util.*; class position { int x; int y; int type; body belong; public static int NOTHING = 0; public static int FREE = 0x01; public static int SNAKE = 0x02; public static int BARRIER = 0x04; public static int FOOD = 0x08; public static int MASK = 0x0F; public position(){} public position(int x, int y) { this.x = x; this.y = y; this.type = position.NOTHING; } public position(int x, int y, int type) { this.x = x; this.y = y; this.type = type; } public int getType(){ return this.type; } public void setType(int type){ this.type = type; } public int getX(){ return this.x; } public int getY(){ return this.y; } public void setBelong(body b){ this.belong = b; } public body getBelong(){ return this.belong; } } /** * 静态数据，保存所有的位置和方向信息 * 这原本是可以定义到各个使用类内部以内部类实现的 * @author marywangran */ class static_pos { public static position LEFT = new position(-1, 0); public static position RIGHT = new position(1, 0); public static position UP = new position(0, -1); public static position DOWN = new position(0, 1); public static position HALT = new position(0, 0); public static position pos[][]; public static void setpos (int width, int height) { int i = 0, j = 0; int num = width*height; pos = new position[width][height]; for (i = 0; i < width; i++) { for (j = 0; j < height; j++) { pos[i][j] = new position(i, j); pos[i][j].setType(position.NOTHING); } } } public static position go_on(position curr, position direct) { return pos[curr.x + direct.x][curr.y + direct.y]; } } /** * 游戏中有些元素是链表，定义为body类 * @author marywangran */ class body extends Object{ position pos; position direct; public body(){} public body (position pos, position direct){ this.pos = pos; this.direct = direct; } public void setPosition(position pos){ this.pos = pos; } public position getPosition(){ return this.pos; } public void setDirect(position direct){ this.direct = direct; } public position getDirect(){ return this.direct; } } /** * 将Snake进行了封装，定义其该有的方法 * @author marywangran */ class Snake { LinkedList snake_body; LinkedList delta_pos; body eat = null; public static int NOTHING = 0; public Snake(int x, int y, int length, position init_dir, int hv) { this.delta_pos = new LinkedList(); this.snake_body = new LinkedList(); for (int i = 0; i < length; i++){ position pos = static_pos.pos[x+i][y]; pos.setType((i == length-1)?position.SNAKE:(position.BARRIER|position.SNAKE)); body sb = new body(pos, init_dir); snake_body.add(0, sb); delta_pos.add(sb.getPosition()); } } public LinkedList getDeltaList(){ return this.delta_pos; } public void removeDeltaList(){ delta_pos.clear(); } public void snakeGoingOn(){ int nx = 0, ny = 0, nType; position opos, npos; body bf = snake_body.get(0); //得到蛇头 bf.getPosition().setType(position.BARRIER); nx = bf.getPosition().getX() + bf.getDirect().getX(); ny = bf.getPosition().getY() + bf.getDirect().getY(); npos = static_pos.pos[nx][ny]; //得到新的蛇头位置 //得到新位置的Type，看看蛇到底碰到了什么 nType = (npos.getType()& position.MASK);//&~position.SNAKE; if(nType == position.BARRIER){ System.out.println("over"); //死了，TODO } else if ((nType & position.FOOD) != 0) { //吃了食物 System.out.println("foodx:"+npos.x+":"+npos.y); npos.setType(position.FREE|position.SNAKE); npos.getBelong().setDirect(bf.getDirect()); this.snake_body.add(0, npos.getBelong()); this.eat = npos.getBelong(); } else { //前行 body bl = snake_body.remove(snake_body.size()-1); opos = bl.getPosition(); opos.setType(position.FREE); static_pos.pos[nx][ny].setType(position.FREE|position.SNAKE); bl.setDirect(bf.getDirect()); bl.setPosition(npos); snake_body.add(0, bl); delta_pos.add(opos); } delta_pos.add(npos); } public body getEatPending(){ return this.eat; } public void clearEat(){ this.eat = null; } public void changeDirect(position direct) { snake_body.get(0).setDirect(direct); } } class Snake_Game_Pad { int curr_status; int curr_level; int curr_score; int width, height; Snake snake; boolean repaintFood = false; LinkedList freelist; LinkedList foodlist; /** * 贪吃蛇游戏初始化 * @param width 横向元素数量 * @param height 纵向元素数量 * @param init_length 初始蛇长度 */ public void init(int width, int height, int init_length) { this.width = width; this.height = height; static_pos.setpos(this.width, this.height); this.snake = new Snake(10, 10, 1, static_pos.RIGHT, 0); this.foodlist = new LinkedList(); freelist = new LinkedList(); //初始化障碍position的Type for (int i = 0; i < this.width; i++){ static_pos.pos[i][0].setType(position.BARRIER); static_pos.pos[i][this.height-1].setType(position.BARRIER); } for (int i = 0; i < this.height; i++){ static_pos.pos[0][i].setType(position.BARRIER); static_pos.pos[this.width -1][i].setType(position.BARRIER); } //初始化freelist for (int i = 0; i < this.width; i++){ for (int j = 0; j < this.height; j++){ if (static_pos.pos[i][j].getType() == position.NOTHING) freelist.add(static_pos.pos[i][j]); } } random_gen_food (); this.repaintFood = true; } public void reset() { freelist.clear(); foodlist.clear(); } /** * 贪吃蛇主处理函数 * @return 需要重绘的free_body元素的链表 */ LinkedList game_handler() { LinkedList delta; snake.snakeGoingOn(); //需要将delta中的新蛇体从freelist删除，将新free加入freelist，此处没有做，为一bug delta = snake.getDeltaList(); if (snake.getEatPending() != null){ position foodeat = snake.getEatPending().getPosition(); foodlist.remove(foodeat); delta.add(foodeat); snake.clearEat(); this.repaintFood = true; this.random_gen_food(); } return delta; } public void afterGoon(){ snake.removeDeltaList(); } public boolean getEatPending(){ return this.repaintFood; } public void clearEatPending(){ this.repaintFood = false; } void key_handler (position direct) { this.snake.changeDirect(direct); } /** * 该方法没有完全实现，现有的实现很丑陋。TODO * 1.将分值设定参数化，策略化，和当前级别联动 * 2.将超时时间和当前级别以及最近距离联动 */ void random_gen_food () { Random rand = new Random(); int rx = rand.nextInt(this.freelist.size()-1); position food = this.freelist.get(rx); body fb = new body(food, static_pos.HALT); fb.getPosition().setType(position.FOOD); fb.getPosition().setBelong(fb); foodlist.add(fb.getPosition()); } void clearFood(position food){ foodlist.clear(); } } /** * 简单的一个UI，测试用的，十分不完善，什么功能都没有 * @author marywangran */ class GameThread extends JFrame implements KeyListener ,Runnable { Snake_Game_Pad game; position pos; JPanel mainp; public GameThread() { static_pos.setpos(200,200); game = new Snake_Game_Pad(); game.init(200, 200, 20); mainp=new JPanel(); mainp.addKeyListener(this); mainp.setFocusable(true); getContentPane().setLayout(null); getContentPane().add(mainp); mainp.setBounds(0,0,650,650); setSize(650,650); setResizable(false); setVisible(true); new Thread(this).start(); } public void prepaint(){ Graphics g = mainp.getGraphics(); this.setBackground(Color.white); int i ,j; for(i=0;i<600;i+=3) for(j=0;j<600;j+=3) { g.setColor(Color.green); g.fillRect(i,j,3,3); } g.setColor(Color.blue); } public void paint(Graphics g) { g = mainp.getGraphics(); Iterator pos_iter = game.game_handler().iterator(); //取得delta链表，仅重画改变了的部分 while (pos_iter.hasNext()){ position pos = pos_iter.next(); if ((pos.getType()&position.SNAKE) != 0){ g.setColor(Color.blue); } else if ((pos.getType()&position.FREE) != 0){ g.setColor(Color.green); } g.fillRect(pos.x*3, pos.y*3,3,3); } //仅在食物位置发生改变的时候才重画食物，一下子重画所有食物 if (game.getEatPending()){ Iterator food_iter = game.foodlist.iterator(); while (food_iter.hasNext()){ position pos = food_iter.next(); g.setColor(Color.red); g.fillRect(pos.x*3, pos.y*3,3,3); }//打印引起的悲哀 game.clearEatPending(); } game.afterGoon(); } public void run () { LinkedList clist = null; while (true) { try { repaint(); Thread.sleep(100); }catch (Exception e) { e.printStackTrace();//System.exit(1); } } } public void keyPressed(KeyEvent ke) { } public void keyReleased(KeyEvent ke) { } public void keyTyped(KeyEvent key) { String kv = ""+key.getKeyChar(); if (kv.equals("w")) game.key_handler(static_pos.UP); else if (kv.equals("s")) game.key_handler(static_pos.DOWN); else if(kv.equals("a")) game.key_handler(static_pos.LEFT); else if(kv.equals("d")) game.key_handler(static_pos.RIGHT); } } public class Main { public static void main(String[] args) { new GameThread(); } }
这个版本的蛇跑起来的话，CPU利用率大大降低，比完全链表版的提高不少，比完全二维数组版的效率提高更多，虽然完全链表版的理解起来更直观，然而此版本的程序CPU执行起来更轻松，孰重孰轻，还是自己权衡。

这是一个真正可玩的版本，然而到此我就再也做不下去了，GUI不是我所长，设计加分/计分/排名逻辑也非我所好，就此打住了，不过我深深知道，这种性格是一个人生致命的缺陷