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php数字游戏 计算24算法

　　本文标签：数字游戏,计算24

算法思路：把每一个数字看做一个独立的数学表达式，表达式之间加上标点符号组合成新表达式，一共组合4次，表达式之间的所有组合可以通过递归来实现.
代码如下：
复制代码 代码如下:

<?php
/**
* A 24 maker
* @version 1.0.0
* @author laruence<laruence at yahoo.com.cn>
* @copyright (c) 2009 http://www.laruence.com
*/
class TwentyFourCal {
public $needle = 24;
public $precision = 1e-6;
function TwentyFourCal() {
}
private function notice($mesg) {
var_dump($mesg);
}
/**
* 取得用户输入方法
*/
public function calculate($operants = array()) {
try {
$this->search($operants, 4);
} catch (Exception $e) {
$this->notice($e->getMessage());
return;
}
$this->notice(can\t compute!);
return;
}
/**
* 求24点算法PHP实现
*/
private function search($expressions, $level) {
if ($level == 1) {
$result = return . $expressions[0] . ;;
if ( abs(eval($result) - $this->needle) <= $this->precision) {
throw new Exception($expressions[0]);
}
}
for ($i=0;$i<$level;$i++) {
for ($j=$i+1;$j<$level;$j++) {
$expLeft = $expressions[$i];
$expRight = $expressions[$j];
$expressions[$j] = $expressions[$level - 1];
$expressions[$i] = ( . $expLeft . + . $expRight . );
$this->search($expressions, $level - 1);
$expressions[$i] = ( . $expLeft . * . $expRight . );
$this->search($expressions, $level - 1);
$expressions[$i] = ( . $expLeft . - . $expRight . );
$this->search($expressions, $level - 1);
$expressions[$i] = ( . $expRight . - . $expLeft . );
$this->search($expressions, $level - 1);
if ($expLeft != 0) {
$expressions[$i] = ( . $expRight . / . $expLeft . );
$this->search($expressions, $level - 1);
}
if ($expRight != 0) {
$expressions[$i] = ( . $expLeft . / . $expRight . );
$this->search($expressions, $level - 1);
}
$expressions[$i] = $expLeft;
$expressions[$j] = $expRight;
}
}
return false;
}
function __destruct() {
}
}
/* demo */
$tf = new TwentyFourCal();
$tf->calculate( array(4,8,8,8) );
?>