Question

有人可以检查一下我的代码，因为在某些情况下，在这段代码中输出是正确的但是当我尝试测试这个输入zzzazzazz时输出不是我所期望的。

npm i hammerjs

Answer 1

您可以提供要检查的字符串作为此函数的参数：

function checkPalindrome($text) {
    //Eliminate punctuation and spaces
    $str = preg_replace('/[^a-z]+/i', '', $text);
    
    // Force lower case
    $str = strtolower($str);
    
    //compare
    $verdict = $str == strrev($str) ? '"' . $text . '" ' . 'is a palindrome' : '"' . $text . '"' . ' is not a palindrome';
    
    return $verdict;
}

echo checkPalindrome("Red rum, sir, is murder");

请参见演示 here 。

Answer 2

如果只有第一个字符匹配最后一个字符，则返回true - 您没有检查其余字符

$ ./check_2chars.sh
match

Answer 3

你的代码到处都是。有很多方法可以解决这个问题，我不认为你甚至需要将字符串拆分成一个字符数组。但是，假设你想这样做，这是一个有效的实现：

repeat :all

Demo

基本思路是从两端开始沿着弦向下走，并逐一比较两侧的字符。如果我们发现两个字符不相同的情况，那么字符串不能是回文。请注意，这种方法涵盖了偶数和奇数长度的回文。在奇数长度回文的情况下，中心字符可以是任何东西，我写的循环甚至不会检查它。

Answer 4

一种更简单的方法，使用strrev()并删除除a-z之外的所有字符然后小写。

<?php
function checkPalindrome($str) {
    $str = strtolower(preg_replace('/[^a-z]+/i', '', $str));
    return $str == strrev($str);
}

// test, few taken from http://www.palindromelist.net
$palindromes = [
    'A but tuba.',    
    'madam',    
    'hannah',    
    'A dog, a plan, a canal: pagoda.',    
    'Nurses run',    
    'A dog! A panic in a pagoda!',    
    'A lad named E. Mandala',    
    'A man, a plan, a canal: Panama.',    
    'A man, a plan, a cat, a ham, a yak, a yam, a hat, a canal-Panama!',    
    'A new order began, a more Roman age bred Rowena.',    
    'Decaf and DNA faced.',    
    'Dennis and Edna sinned.',    
    'Devil never even lived.',    
    'Dr. Awkward',    
    'On a clover, if alive, erupts a vast, pure evil; a fire volcano.',    
    'See, slave, I demonstrate yet arts no medieval sees.',    
    'Star? Come, Donna Melba, I’m an amiable man – no Democrats!',    
    'Swap God for a janitor; rot in a jar of dog paws.',    
];

foreach ($palindromes as $str) {
    echo $str.(checkPalindrome($str) ? ' is' : 'is not').' a palindrome'.PHP_EOL;
}

https://3v4l.org/tuHnU

<强>结果：

A but tuba. is a palindrome
madam is a palindrome
hannah is a palindrome
A dog, a plan, a canal: pagoda. is a palindrome
Nurses run is a palindrome
A dog! A panic in a pagoda! is a palindrome
A lad named E. Mandala is a palindrome
A man, a plan, a canal: Panama. is a palindrome
A man, a plan, a cat, a ham, a yak, a yam, a hat, a canal-Panama! is a palindrome
A new order began, a more Roman age bred Rowena. is a palindrome
Decaf and DNA faced. is a palindrome
Dennis and Edna sinned. is a palindrome
Devil never even lived. is a palindrome
Dr. Awkward is a palindrome
On a clover, if alive, erupts a vast, pure evil; a fire volcano. is a palindrome
See, slave, I demonstrate yet arts no medieval sees. is a palindrome
Star? Come, Donna Melba, I’m an amiable man – no Democrats! is a palindrome
Swap God for a janitor; rot in a jar of dog paws. is a palindrome

Palindrome php有些案例是对的，有些是错的

4 个答案:

Demo