数据结构和算法系列课程（02） --- 线性表和贪吃蛇
线性结构是一种具有以下特点的结构：
- 存在唯一一个被称为“第一个”的数据元素
- 存在唯一一个被称为“最后一个”的数据元素
- 除第一个元素之外，集合中的每个元素均有且仅有一个前驱
- 除最后一个元素之外，集合中的每个元素均有且仅有一个后继
那么，线性表、栈、队列、数组、字符串都可以视为线性结构。
线性表是N个数据元素的有限序列，关于这部分的内容可以参考我的数据结构的课件，下面是下载地址：
http://download.csdn.net/detail/jackfrued/6200903
按照面向接口编程的思想，我们先通过一个接口为线性表拟定相应的方法，然后给出基于数组和基于链式结构的两种实现方式。
/**
* 线性表接口
* @author 骆昊
*
* @param 泛型参数 - 线性表存储的元素类型
*/
public interface MyList {
/**
* 获取指定位置的元素
* @param index 索引
* @return 索引对应的元素
*/
public T get(int index);
/**
* 为指定位置的元素设置值
* @param t 新元素
* @param index 索引
*/
public void set(T t, int index);
/**
* 添加元素
* @param t 待添加的元素
*/
public void add(T t) ;
/**
* 在线性表的指定位置添加元素
* @param t 待添加的元素
* @param index 指定的位置
*/
public void add(T t, int index);
/**
* 删除元素
* @param index 删除元素的位置
* @return 被删除的元素
*/
public T remove(int index);
/**
* 删除指定的元素
* @param t 待删除的元素
* @return 删除成功返回true否则返回false
*/
public boolean remove(T t);
/**
* 找出第一个与指定元素匹配的元素的位置
* @param t 待匹配元素
* @return 找到了返回元素位置, 未找到返回-1
*/
public int indexOf(T t);
/**
* 获取线性表中元素个数
* @return 元素个数
*/
public int size();
/**
* 清空线性表
*/
public void clear();
/**
* 判断线性表是否为空
* @return 没有元素返回true有元素返回false
*/
public boolean isEmpty();
}
public abstract class MyAbstractList implements MyList {
protected int size;
@Override
public void add(T t) {
add(t, size);
}
@Override
public boolean isEmpty() {
return size == 0;
}
@Override
public int size() {
return size;
}
@Override
public synchronized boolean remove(T t) {
int index = indexOf(t);
if(index >= 0) {
remove(index);
return true;
}
return false;
}
} import java.util.Arrays;
/**
* 自定义线性表(通过数组实现)
* @author Hao
*
* @param 泛型参数(线性表存储元素的类型)
*/
public class MyArrayList extends MyAbstractList {
private T[] content = null;
private int capacity; // 容量
private int size; // 有多少个元素
private double factor; // 空间追加因子(0~1)
public MyArrayList() {
this(50, 0.5);
}
public MyArrayList(double factor) {
this(50, factor);
}
public MyArrayList(int capacity) {
this(capacity, 0.5);
}
@SuppressWarnings("unchecked")
public MyArrayList(int capacity, double factor) {
content = (T[]) new Object[capacity];
this.capacity = capacity;
this.factor = factor;
this.size = 0;
}
public T get(int index) {
if(index >= 0 && index < size) {
return content[index];
}
else {
throw new RuntimeException("下标越界: " + index);
}
}
public synchronized void add(T t, int index) {
if(index >= 0 && index <= size) {
if(size >= capacity) {
ensureCapacity();
}
for(int i = size - 1; i >= index; i--) {
content[i + 1] = content[i];
}
content[index] = t;
size++;
}
else {
throw new RuntimeException("下标越界: " + index);
}
}
private void ensureCapacity() {
capacity += (int)(capacity * factor);
content = Arrays.copyOf(content, capacity);
}
public synchronized T remove(int index) {
if(index >= size || index < 0) {
throw new IndexOutOfBoundsException("下标越界: " + index);
}
T temp = content[index];
for(int i = index; i < size; i++) {
content[i] = content[i + 1];
}
size--;
return temp;
}
public void clear() {
size = 0;
}
@Override
public synchronized void set(T t, int index) {
if(index >= size || index < 0) {
throw new IndexOutOfBoundsException("下标越界: " + index);
}
content[index] = t;
}
@Override
public int indexOf(T t) {
for(int i = 0; i < size; i++) {
if(content[i].equals(t)) {
return i;
}
}
return -1;
}
} 链式实现方式 - 链表
public class MyLinkedList extends MyAbstractList {
private ListNode head, tail;
private class ListNode {
public T element;
public ListNode next;
public ListNode(T element) {
this.element = element;
}
}
public synchronized T get(int index) {
if (index < 0 || index >= size) {
throw new RuntimeException("下标越界: " + index);
}
ListNode curr = head;
for (int i = 0; i < index; i++) {
curr = curr.next;
}
return curr.element;
}
public synchronized void addFirst(T t) {
ListNode newNode = new ListNode(t);
newNode.next = head;
head = newNode;
size++;
if (tail == null) {
tail = head;
}
}
public synchronized void addLast(T t) {
if (tail == null) {
head = tail = new ListNode(t);
} else {
tail.next = new ListNode(t);
tail = tail.next;
}
size++;
}
public synchronized void add(T t, int index) {
if (index < 0 || index > size) {
throw new RuntimeException("下标越界: " + index);
} else {
if (index == 0) {
addFirst(t);
} else if (index == size) {
addLast(t);
} else {
ListNode curr = head;
for (int i = 1; i < index; i++) {
curr = curr.next;
}
ListNode temp = curr.next;
curr.next = new ListNode(t);
curr.next.next = temp;
size++;
}
}
}
public synchronized T remove(int index) {
if (index < 0 || index >= size) {
throw new RuntimeException("下标越界: " + index);
} else if (index == 0) {
return removeFirst();
} else if (index == size - 1) {
return removeLast();
} else {
ListNode prev = head;
for (int i = 1; i < index; i++) {
prev = prev.next;
}
ListNode curr = prev.next;
prev.next = curr.next;
size--;
return curr.element;
}
}
public synchronized T removeFirst() {
T temp = null;
if (head != null) {
temp = head.element;
head = head.next;
size--;
if(head == null) {
tail = null;
}
}
return temp;
}
public synchronized T removeLast() {
T temp = null;
if (tail != null) {
ListNode prev = head;
if(prev == tail) {
temp = prev.element;
head = tail = null;
}
else {
while(prev.next != tail) {
prev = prev.next;
}
temp = prev.next.element;
prev.next = null;
tail = prev;
}
size--;
}
return temp;
}
public void clear() {
head = tail = null;
}
@Override
public void set(T t, int index) {
if (index < 0 || index >= size) {
throw new RuntimeException("下标越界: " + index);
}
ListNode curr = head;
for (int i = 0; i < index; i++) {
curr = curr.next;
}
curr.element = t;
}
@Override
public int indexOf(T t) {
if(head != null) {
ListNode curr = head;
for (int i = 0; i < size; i++) {
if(curr.element.equals(t)) {
return i;
}
curr = curr.next;
}
}
return -1;
}
}
好了，到这里可以用链表来实现一个贪吃蛇游戏，其中的关键就是蛇吃到蛋以后如何加长。如果用链表来存储蛇身上的每个节点，那么可以通过在头或尾添加节点的方式来实现蛇的增长。同理，如果要让蛇移动，也可以通过删除尾部节点和添加头部节点来实现，也就是说利用链表提供的操作可以很容易的实现一个贪吃蛇游戏，代码如下所示：
先定义蛇身上的每一个节点：
import java.awt.Color;
import java.awt.Graphics;
public class SnakeNode {
private int size = 10;
private int row, col;
public SnakeNode(int row, int col) {
this.row = row;
this.col = col;
}
public int getRow() {
return row;
}
public void setRow(int row) {
this.row = row;
}
public int getCol() {
return col;
}
public void setCol(int col) {
this.col = col;
}
public void draw(Graphics g) {
g.setColor(Color.GREEN);
g.fillRect(col * size, row * size, size, size);
}
}
import java.awt.Graphics;
import java.awt.Rectangle;
import com.accp.util.MyLinkedList;
import com.accp.util.MyList;
public class Snake {
private MyLinkedList list = new MyLinkedList();
private Direction dir = Direction.LEFT;
private boolean alive = true;
public Snake() {
list.addLast(new SnakeNode(30, 30));
list.addLast(new SnakeNode(30, 31));
list.addLast(new SnakeNode(30, 32));
list.addLast(new SnakeNode(30, 33));
list.addLast(new SnakeNode(30, 34));
}
public Direction getDir() {
return dir;
}
public MyList getBody() {
return list;
}
public boolean isAlive() {
return alive;
}
public void setAlive(boolean alive) {
this.alive = alive;
}
public SnakeNode getHead() {
return list.get(0);
}
public void move() {
increaseLength();
list.removeLast();
}
public void changeDirection(char ch) {
switch (ch) {
case 'w':
case 'W':
if (dir != Direction.DOWN) {
dir = Direction.UP;
}
break;
case 's':
case 'S':
if (dir != Direction.UP) {
dir = Direction.DOWN;
}
break;
case 'a':
case 'A':
if (dir != Direction.RIGHT) {
dir = Direction.LEFT;
}
break;
case 'd':
case 'D':
if (dir != Direction.LEFT) {
dir = Direction.RIGHT;
}
break;
}
}
public void draw(Graphics g) {
for (int i = 0; i < list.size(); i++) {
list.get(i).draw(g);
}
}
public Rectangle getRectangle() {
SnakeNode head = list.get(0);
return new Rectangle(head.getCol() * 10, head.getRow() * 10, 10, 10);
}
public void eatEgg() {
increaseLength();
increaseLength();
}
private void increaseLength() {
SnakeNode snakeHead = list.get(0);
int row = snakeHead.getRow();
int col = snakeHead.getCol();
switch (dir) {
case UP:
row = row - 1;
break;
case DOWN:
row = row + 1;
break;
case LEFT:
col = col - 1;
break;
case RIGHT:
col = col + 1;
break;
}
SnakeNode newHead = new SnakeNode(row, col);
list.addFirst(newHead);
}
}
public enum Direction {
LEFT, RIGHT, UP, DOWN;
}
游戏主窗体：
import java.awt.Color;
import java.awt.Graphics;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;
import java.awt.image.BufferedImage;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import com.accp.util.MyList;
@SuppressWarnings("serial")
public class GameFrame extends JFrame {
private Snake s = new Snake();
private Wall w = new Wall();
private Egg e = null;
private char oldKey = '#';
private BufferedImage image =
new BufferedImage(600, 600, BufferedImage.TYPE_INT_RGB);
private Egg makeAnEgg() {
int row = (int) (Math.random() * 40 + 10);
int col = (int) (Math.random() * 40 + 10);
return new Egg(row, col);
}
public GameFrame() {
e = makeAnEgg();
this.setSize(600, 600);
this.setResizable(false);
this.setLocationRelativeTo(null);
this.setDefaultCloseOperation(EXIT_ON_CLOSE);
this.addKeyListener(new KeyAdapter() {
@Override
public void keyPressed(KeyEvent e) {
char ch = e.getKeyChar();
if(ch != oldKey) { // �������
oldKey = ch;
s.changeDirection(ch);
}
}
});
new Thread(new Runnable() {
@Override
public void run() {
while(true) {
if(s.isAlive()) {
s.move();
if(e != null) {
if(e.getRow() == s.getHead().getRow() && e.getCol() ==
s.getHead().getCol()) {
s.eatEgg();
e = makeAnEgg();
}
}
SnakeNode snakeHead = s.getHead();
int row = snakeHead.getRow();
int col = snakeHead.getCol();
if(row <= 5 || row >= 55 || col <= 5 || col >= 55) {
s.setAlive(false);
}
MyList snakeBody = s.getBody();
for(int i = 1; i < snakeBody.size(); i++) {
SnakeNode node = snakeBody.get(i);
if(node.getRow() == row && node.getCol() == col) {
s.setAlive(false);
break;
}
}
if(!s.isAlive()) {
JOptionPane.showMessageDialog(null, "Game Over!!!");
}
try {
Thread.sleep(200);
}
catch (InterruptedException e) {
}
repaint();
}
}
}
}).start();
}
@Override
public void paint(Graphics g) {
//super.paint(g);
Graphics offG = image.getGraphics();
offG.setColor(new Color(0xffff80));
offG.fillRect(0, 0, 600, 600);
w.draw(offG);
s.draw(offG);
if(e != null) {
e.draw(offG);
}
g.drawImage(image, 0, 0, null);
}
public static void main(String[] args) {
new GameFrame().setVisible(true);
}
}
当然，这个游戏还少不了墙和蛋，代码如下：
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Rectangle;
/**
* 砖块
* @author 骆昊
*
*/
public class Brick {
private int row, col;
private int size = 10;
public Brick(int row, int col) {
this.row = row;
this.col = col;
}
public void draw(Graphics g) {
g.setColor(new Color(64, 0, 0));
g.fillRect(col * size, row * size, size, size);
}
public Rectangle getRectangle() {
return new Rectangle(col * size, row * size, size, size);
}
}import java.awt.Graphics;
import java.util.ArrayList;
import java.util.List;
/**
* 围墙
* @author 骆昊
*
*/
public class Wall {
private List list = new ArrayList();
public Wall() {
for(int i = 5; i <= 55; i++) {
list.add(new Brick(5, i)); // -
list.add(new Brick(i, 5)); // |
list.add(new Brick(55, i)); // -
list.add(new Brick(i, 55)); // |
}
}
public List getAllBricks() {
return list;
}
public void draw(Graphics g) {
for(Brick b : list) {
b.draw(g);
}
}
} import java.awt.Color;
import java.awt.Graphics;
/**
* 蛋
* @author 骆昊
*
*/
public class Egg {
private int col, row;
private int size = 10;
public Egg(int col, int row) {
this.row = row;
this.col = col;
}
public int getCol() {
return col;
}
public void setCol(int col) {
this.col = col;
}
public int getRow() {
return row;
}
public void setRow(int row) {
this.row = row;
}
public void draw(Graphics g) {
g.setColor(Color.RED);
g.fillOval(col * size, row * size, size, size);
}
}
好了，到这里一个贪吃蛇游戏就做好了，这个游戏的碰撞检测非常简单，因为蛇和蛋还有墙都在格子里（虽然没有绘制出来），通过横纵坐标的比较就可以完成了。