PHP method to find the palindrome number in a range and the square root is also a palindrome number-PHP Tutorial-php.cn

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PHP method to find the palindrome number in a range and the square root is also a palindrome number

Dec 26, 2017 am 10:58 AM

php square root within range

How to find the palindrome number in a range and the square root is also a palindrome number in php? This article mainly introduces the method of PHP to find the number of palindromes in a specified range and the square root is also a palindrome number. It analyzes PHP's technique of judging palindromes through examples. I hope to be helpful.

The example of this article describes the method of PHP to find the palindrome number in the specified range and the square root is also a palindrome number. Share it with everyone for your reference. The details are as follows:

1. Requirements:

Given two values X and Y, count the number of palindromes in this interval, and require that their square roots are also palindromes. Among them 1<= x <= y < 10 14

2. Solution:

&lt;?php
error_reporting(E_ALL);
ini_set(&quot;display_errors&quot;, 1);
//避免超时
set_time_limit(0);
$t1=microtime();
function isPlalindrome($num){
  $str=&quot;$num&quot;;
  $len=strlen($num);
  $k = intval($len/2) + 1;//获取中间位数
  for($j=0;$j&lt;$k;$j++){
    if($str{$j}!=$str{$len-1-$j}){ 
      return false;
    }
  } 
  return true;
}
function showPlalindrome($min,$max){
//因为要计算在$min,$max间的回文数且其自身平方根也是回文数
//所以相当于求一sqrt($min)~sqrt($max)间数
//其平方在$min~$max间也是回文数
//$min~$max是连续正整数，所以可以这样缩小很多计算量，否则……
  $start=sqrt($min);
  $end=sqrt($max);
  for($i=$start;$i&lt;$end;$i++){
    if(isPlalindrome($i) &amp;&amp;isPlalindrome($n=$i*$i) ){
     echo $n.&quot; &lt;br/&gt;&quot;;
    }
  }
}
showPlalindrome(1,100000000000000);
$t2=microtime();
$starttime = explode(&quot; &quot;,$t1);
$endtime = explode(&quot; &quot;,$t2);
$totaltime = $endtime[0]-$starttime[0]+$endtime[1]-$starttime[1];
$timecost = sprintf(&quot;%s&quot;,$totaltime);
echo &quot;页面运行时间: $timecost 秒&quot;;
?&gt;

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