使用Java实现alpha-beta剪枝算法（井字棋小游戏）
1、初始化游戏界面：
/**
* 初始化游戏界面：
*/
public void StartGream() {
for (int i = 1; i < 4; i++)
for (int j = 1; j < 4; j++)
chess[i][j] = '-';
//首先让用户选择使用的符号：X/O,1为X,2为O
System.out.println("欢迎您来到本游戏界面");
System.out.println("请您选择您的游戏符号:X/O,输入数字1为X,数字2为O！");
Scanner in = new Scanner(System.in);
int a = in.nextInt();
if (a == 1) {
player = 'X';
computer = 'O';
} else if (a == 2) {
player = 'O';
computer = 'X';
} else {
player = 'X';
computer = 'O';
System.out.println("输入错误字符，默认玩家字符为X");
}
//开始选择谁先手，玩家先手，还是机器先手？
System.out.println("请您选择是否先手？先手请按数字1，否则请按数字2！");
Scanner in1 = new Scanner(System.in);
int b = in1.nextInt();
if (b == 1) {
//玩家先手，画井字棋盘
Print();
} else if (b == 2) {
//开局随便下
Random rand = new Random();
int row = rand.nextInt(3) + 1;
int col = rand.nextInt(3) + 1;
chess[row][col] = computer;
Print();
} else {
System.out.println("输入错误字符，默认玩家先手！");
Print();
}
}2、画棋盘
/**
* 画棋盘
*/
void Print() {
System.out.println("**********");
for (int i = 1; i < 4; i++) {
for (int j = 1; j < 4; j++) {
System.out.print("| ");
System.out.print(chess[i][j] + " ");
if (j == 3) System.out.println("|");
}
if (i == 3) System.out.println("**********");
}
}3、判断赢的条件，有八种
/**
* 判断赢的条件，有八种
* 返回1赢，返回2输
*/
public Boolean Win(char player) {
//：—|连线六种方法
if (chess[1][1] == player && chess[1][2] == player && chess[1][3] == player) {
return true;
}
if (chess[2][1] == player && chess[2][2] == player && chess[2][3] == player) {
return true;
}
if (chess[3][1] == player && chess[3][2] == player && chess[3][3] == player) {
return true;
}
if (chess[1][1] == player && chess[2][1] == player && chess[3][1] == player) {
return true;
}
if (chess[1][2] == player && chess[2][2] == player && chess[3][2] == player) {
return true;
}
if (chess[1][3] == player && chess[2][3] == player && chess[3][3] == player) {
return true;
}
//斜着三点连一线俩种方法
if (chess[1][1] == player && chess[2][2] == player && chess[3][3] == player) {
return true;
}
if (chess[1][3] == player && chess[2][2] == player && chess[3][1] == player) {
return true;
}
return false;
}4、判断棋子是否还有地方下？
//判断棋盘是否还有地方能下棋子
public boolean isEmpty() {//判断棋盘是否为空
for (int i = 1; i < 4; i++) {
for (int j = 1; j < 4; j++) {
if (chess[i][j] == '-') return false;
}
}
return true;
}5、玩家开始下棋
//玩家开始下棋
public void playerGo() {
System.out.println("--------------------------：1，2，3");
System.out.println("该您走啦，请您输入棋子位置：4，5，6");
System.out.println("--------------------------：7，8，9");
int row, col;
Scanner in = new Scanner(System.in);
int a = in.nextInt();
if (a >= 1 && a <= 9) {
if (a % 3 == 0) row = a / 3;
else row = a / 3 + 1;
col = a - 3 * (row - 1);
if (chess[row][col] != '-') {
System.out.println("该位置已有棋子");
playerGo();
}
chess[row][col] = player;
Print();
} else {
System.out.println("您的字符输入错误，请您重新输入！");
playerGo();
}
}
6、电脑开始下棋
//电脑开始下棋
public void computerGo() throws InterruptedException {
int best = 0;
int bestScore = -1000;
int score;
for (int i = 1; i <= 3; i++) {
for (int j = 1; j <= 3; j++) {
if (chess[i][j] == '-') {
chess[i][j] = computer;
score = bestInput("player", "computer", -1000, 1000);//alpha-beta剪枝是一个根据上下界限剪枝的算法，初始的上下界限为无穷
if (score >=bestScore) {//在同一层的节点里面需要不断试探性递归，用回溯法找到最合适的下棋点使自己胜算最大
bestScore = score;
best = (i - 1) * 3 + j;
}
chess[i][j] = '-';
}
}
}
int row, col;
if (best % 3 == 0) row = best / 3;
else row = best / 3 + 1;
col = best - (row - 1) * 3;
chess[row][col] = computer;
Thread.sleep(2000);
Print();
}7、//剪枝算法（-1玩家赢，1电脑赢，0平局）
//剪枝算法（-1玩家赢，1电脑赢，0平局）
int bestInput(String state, String nextState, int alpha, int beta) {//输入，调用剪枝的过程
char ch;
if (state.equals("computer")) {
ch = computer;
} else {
ch = player;
}
if (Win(ch)) {
if (state.equals("computer")) {
//电脑赢
return 1;
} else {
//玩家赢
return -1;
}
} else if (isEmpty()) {
//平局
// System.out.println("平局！");
return 0;
} else {
int score;
for (int i = 1; i < 4; i++) {
for (int j = 1; j < 4; j++) {
if (chess[i][j] == '-') {
chess[i][j] = ch;
score = bestInput(nextState, state, alpha, beta);
chess[i][j] = '-';
if (state.equals("computer")) {
if (score >= alpha) {
alpha = score;
}
if (alpha > beta) {
return beta;
}
} else {
if (score < beta) {
beta = score;
}
if (beta <= alpha) {
return alpha;
}
}
}
}
}
if (state.equals("computer")) {
return alpha;
} else {
return beta;
}
}
}8、启动main
private char[][] chess = new char[4][4];
private char player;
private char computer;
public static void main(String[] args) throws InterruptedException {
Main main = new Main();
main.StartGream();
String current = "player";
while (!main.Win(main.computer) && !main.Win(main.player) && !main.isEmpty()) {//终止条件是当前棋盘为空或者有一方胜利
switch (current) {
case "player":
main.playerGo();
current = "computer";
break;//当玩家下完后轮到电脑下
case "computer":
main.computerGo();
current = "player";
break;
default:
break;
}
}
if (main.Win(main.computer)) {
System.out.println("电脑胜利！");
} else if (main.Win(main.player)) {
System.out.println("玩家胜利");
} else {
System.out.println("平局！");
}
}9、运行结果展示：
