<html> <body> <title>计算结果</title> <?php error_reporting(E_ALL ^ E_NOTICE);
$a = $_POST["a"]; $b = $_POST["b"]; $c = $_POST["c"]; $d = $_POST["d"];
set_time_limit(0); $values = array($a, $b, $c, $d); $result = 24;
$list = array();
echo "<pre>"; makeValue($values); print_r($list);
function makeValue($values, $set=array()) { $words = array("+", "-", "*", "/"); if(sizeof($values)==1) { $set[] = array_shift($values); return makeSpecial($set); }
foreach($values as $key=>$value) { $tmpValues = $values; unset($tmpValues[$key]); foreach($words as $word) { makeValue($tmpValues, array_merge($set, array($value, $word))); } } }
function makeSpecial($set) { $size = sizeof($set);
if($size<=3 || !in_array("/", $set) && !in_array("*", $set)) { return makeResult($set); }
for($len=3; $len<$size-1; $len+=2) { for($start=0; $start<$size-1; $start+=2) { if(!($set[$start-1]=="*" || $set[$start-1]=="/" || $set[$start+$len]=="*" || $set[$start+$len]=="/")) continue; $subSet = array_slice($set, $start, $len); if(!in_array("+", $subSet) && !in_array("-", $subSet)) continue; $tmpSet = $set; array_splice($tmpSet, $start, $len-1); $tmpSet[$start] = "(".implode("", $subSet).")"; makeSpecial($tmpSet); } } }
function makeResult($set) { global $result, $list; $str = implode("", $set); @eval("\$num=$str;"); if($num==$result && !in_array($str, $list)) $list[] = $str; } echo "<pre>"; ?>
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