JavaScript通過極大極小值算法實現AI井字棋遊戲

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話不多說直接上運行截圖：

黑棋是玩傢的位置，紅色方是電腦。電腦會根據當前棋盤的情況選擇一個對自己有利卻對玩傢不利的情況。

算法可以實現電腦勝利，或者電腦和玩傢平局。

代碼如下：

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>井字棋AI</title>
<style>
	.title {
		text-align: center;
	}
	
	.chess {
		display: block;
		/*變成塊級元素，使用margin居中*/
		margin: 50px auto;
		box-shadow: 5px 5px 5px #B9B9B9, -2px -2px 2px #EFEFEF;
		cursor: pointer;
	}
	
	div {
		text-align: center;
	}
	
	.restart {
		padding: 10px 20px;
		background-color: #EE82EE;
		border-radius: 5px;
		color: white;
		cursor: pointer;
	}
</style>
</head>
 
<body>
	<h3 class="title">--井字棋--</h3>
	<canvas class="chess" width="450px" height="450px"></canvas>
	<div>
		<a class="restart" onclick="rst()">重新開始</a>
	</div>
</body>
 
<script>
	var chess = document.getElementsByClassName("chess")[0];
	var title = document.getElementsByClassName("title")[0];
	var context = chess.getContext("2d");
	context.strokeStyle = "#B9B9B9"
 
	window.onload = function() {
		drawChessBoard();
		Init()
	}
 
	function drawChessBoard() {
		for(var i = 0; i < 4; i++) {
			//設置橫線起始點坐標
			context.moveTo(15, 15 + i * 140)
			//設置橫線結束點坐標
			context.lineTo(435, 15 + i * 140)
			//連接2點
			context.stroke();
			//設置豎線
			context.moveTo(15 + i * 140, 15)
			//設置橫線結束點坐標
			context.lineTo(15 + i * 140, 435)
			//連接2點
			context.stroke();
		}
	}
 
	//定義二維數組標記棋子
	var chessboard = []
	for(var i = 0; i < 4; i++) {
		chessboard[i] = [];
		for(var j = 0; j < 4; j++) {
			chessboard[i][j] = 0;
		}
	}
 
	const NUMBER = 3
	const STEP = 9
	const MAN = 1
	const COMPUTER = -1
	const SEARCHDEPTH = 9
	const INT_MAX = 999999
	const INT_MIN = -1000000
 
	var player = 0
	var isGameOver = false
	var currentDepth = 0
	var bestPosition = {
		x: 0,
		y: 0
	}
 
	function Init() {
		for(let i = 0; i < NUMBER; i++) {
			for(let j = 0; j < NUMBER; j++) {
				chessboard[i][j] = 0
			}
		}
		player = MAN
		isGameOver = false
		currentDepth = 0
	}
 
	function isEnd() {
		let i = 0
		let j = 0
		var count = 0
		for(i = 0; i < NUMBER; i++) { //行
			count = 0;
			for(j = 0; j < NUMBER; j++)
				count += chessboard[i][j];
			if(count == 3 || count == -3)
				return count / 3;
		}
		for(j = 0; j < NUMBER; j++) { //列
			count = 0;
			for(i = 0; i < NUMBER; i++)
				count += chessboard[i][j];
			if(count == 3 || count == -3)
				return count / 3;
		}
		count = 0;
		count = chessboard[0][0] + chessboard[1][1] + chessboard[2][2];
		if(count == 3 || count == -3)
			return count / 3;
		count = chessboard[0][2] + chessboard[1][1] + chessboard[2][0];
		if(count == 3 || count == -3)
			return count / 3;
		return 0;
	}
 
	function MaxMinSearch(depth) {
		var value = 0;
		if(player == MAN) value = INT_MIN;
		if(player == COMPUTER) value = INT_MAX;
		if(isEnd() != 0) {
			return Evaluate();
		}
		if(depth == SEARCHDEPTH) {
			value = Evaluate();
			return value;
		}
 
		for(let i = 0; i < NUMBER; i++) {
			for(let j = 0; j < NUMBER; j++) {
				if(chessboard[i][j] == 0) {
					if(player == MAN) {
						chessboard[i][j] = MAN;
						player = COMPUTER;
						var nextvalue = MaxMinSearch(depth + 1);
						player = MAN;
						if(value < nextvalue) {
							value = nextvalue;
							if(depth == currentDepth) {
								bestPosition.x = i;
								bestPosition.y = j;
							}
 
						}
 
					} else if(player == COMPUTER) {
						chessboard[i][j] = COMPUTER;
						player = MAN;
						var nextvalue = MaxMinSearch(depth + 1);
						player = COMPUTER;
						if(value > nextvalue) {
							value = nextvalue;
							if(depth == currentDepth) {
								bestPosition.x = i;
								bestPosition.y = j;
							}
 
						}
					}
					chessboard[i][j] = 0;
				}
 
			}
		}
 
		return value;
	}
	function Logic(){
		if (isGameOver) {
			if (isEnd() == MAN) {
				alert("遊戲結束 玩傢勝利")
			} else if (isEnd() == COMPUTER) {
				alert("遊戲結束 電腦勝利")
			} else {
				alert("遊戲結束 平局")
			}
		}
	}
 
	function Evaluate() {
		var value = isEnd();
		if(value == MAN) return INT_MAX;
		if(value == COMPUTER) return INT_MIN;
	}
 
	chess.onclick = function(event) {
		if(player != MAN) {
			return;
		}
		//獲取坐標
		var x = event.offsetX;
		var y = event.offsetY;
 
		x = Math.trunc((x - 15) / 140)
		y = Math.trunc((y - 15) / 140)
 
		ManPlay(x, y)
		if(isEnd() == 0 && currentDepth < 8) {
			ComputerPlay()
			if(isEnd() != 0) {
				isGameOver = true
			}
		} else {
			isGameOver = true
		}
		Logic()
	}
 
	function ManPlay(x, y) {
		chessboard[x][y] = MAN
		DrawBroad(x,y,MAN)
		currentDepth++
		player = COMPUTER
	}
 
	function ComputerPlay() {
		MaxMinSearch(currentDepth)
		chessboard[bestPosition.x][bestPosition.y] = COMPUTER
		DrawBroad(bestPosition.x,bestPosition.y,COMPUTER)
		currentDepth++
		player = MAN
	}
 
	//落子時繪畫棋盤
	function DrawBroad(i, j, player) {
		context.beginPath();
		context.arc(85 + i * 140, 85 + j * 140, 40, 0, 2 * Math.PI); //畫圓
		context.closePath();
 
		var color;
		if(player == MAN) {
			color = "#000";
		} else {
			color = "red"
		}
		context.fillStyle = color;
		context.fill();
	}
 
	function rst() {
		window.location.reload();
	}
</script>
 
</html>

其中，代碼的242行和244行中的

context.beginPath();
context.arc(85 + i * 140, 85 + j * 140, 40, 0, 2 * Math.PI); //畫圓
context.closePath();

分別是落筆和抬筆的操作。這樣可以避免canvas上畫圓時路徑相連的問題。 

到此這篇關於JavaScript通過極大極小值算法實現AI井字棋遊戲的文章就介紹到這瞭,更多相關JavaScript井字棋遊戲內容請搜索WalkonNet以前的文章或繼續瀏覽下面的相關文章希望大傢以後多多支持WalkonNet！

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