求: 三个5,一个1组成的数学表达式的结果=24, 结果:(5-1/5)*5=24
set_time_limit(0);
$values = array(1, 5, 5, 5);
$result = 24;
$list = array();
echo "
";<br> makeValue($values);<br> print_r($list);<p><span>立即学习</span>“<a href="https://pan.quark.cn/s/7fc7563c4182" style="text-decoration: underline !important; color: blue; font-weight: bolder;" rel="nofollow" target="_blank">PHP免费学习笔记（深入）</a>”；</p><p> function makeValue($values, $set=array())<br> {<br> $words = array("+", "-", "*", "/");<br> if(sizeof($values)==1)<br> {<br> $set[] = array_shift($values);<br> return makeSpecial($set);<br> }<br> foreach($values as $key=>$value)<br> {<br> $tmpValues = $values;<br> unset($tmpValues[$key]);<br> foreach($words as $word)<br> {<br> makeValue($tmpValues, array_merge($set, array($value, $word)));<br> }<br> }<br> } <br> <br> function makeSpecial($set)<br> {<br> $size = sizeof($set);</p><p> if($size {<br> return makeResult($set);<br> }</p><p> for($len=3; $len {<br> for($start=0; $start {<br> if(!($set[$start-1]=="*" || $set[$start-1]=="/" || $set[$start+$len]=="*" || $set[$start+$len]=="/"))<br> continue;<br> $subSet = array_slice($set, $start, $len);<br> if(!in_array("+", $subSet) && !in_array("-", $subSet))<br> continue;<br> $tmpSet = $set;<br> array_splice($tmpSet, $start, $len-1);<br> $tmpSet[$start] = "(".implode("", $subSet).")";<br> makeSpecial($tmpSet); <br> }<br> }<br> } </p><p><br> function makeResult($set)<br> {<br> global $result, $list;<br> $str = implode("", $set);<br> @eval("\$num=$str;");<br> if($num==$result && !in_array($str, $list))<br> $list[] = $str;<br> } </p><p>?><br></p><p style="width:100%;text-align:center;margin:10px 0">
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