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OSystem.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(puter) && !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":puterGo();current = "player";break;default:break;}}if (main.Win(puter)) {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：