用PHP求解最长公共子串问题
<?php
class LCS{
public static function main(){
//设置字符串长度
$substringLength1 = 20;
$substringLength2 = 20; //具体大小可自行设置
$opt=array_fill(0,21,array_fill(0,21,null));
// 随机生成字符串
$x = self::GetRandomStrings($substringLength1);
$y = self::GetRandomStrings($substringLength2);
$startTime = microtime(true);
// 动态规划计算所有子问题
for ($i = $substringLength1 - 1; $i >= 0; $i--){
for ($j = $substringLength2 - 1; $j >= 0; $j--){
if ($x[$i] == $y[$j])
$opt[$i][$j] = $opt[$i + 1][$j + 1] + 1;
else
$opt[$i][$j] = max($opt[$i + 1][$j], $opt[$i][$j + 1]);
}
}
echo "substring1:".$x."\r\n";
echo "substring2:".$y."\r\n";
echo "LCS:";
$i = 0;
$j = 0;
while ($i < $substringLength1 && $j < $substringLength2){
if ($x[$i] == $y[$j]){
echo $x[$i];
$i++;
$j++;
} else if ($opt[$i + 1][$j] >= $opt[$i][$j + 1])
$i++;
else
$j++;
}
$endTime = microtime(true);
echo "\r\n";
echo "Totle time is " . ($endTime - $startTime) . " s";
}
public static function GetRandomStrings($length){
$buffer = "abcdefghijklmnopqrstuvwxyz";
$str="";
for($i=0;$i<$length;$i++){
$random=rand(0,strlen($buffer)-1);
$str.=$buffer[$random];
}
return $str;
}
}
LCS::main();
?>
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