如何识别两个字符串是否构成回文对？

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回文，英文 palindrome，如果一个字符串的反转与原始字符串相同，则该字符串称为回文字符串。例如：radar, level, Able was I ere I saw Elba。反转字符串与原始字符串比较，反转字符串或数字，并输出反转。例如：反转字符串与原始字符串比较，反转字符串或数字：radar -> radar，level -> level，Able was I ere I saw Elba -> Able was I ere I saw Elba。

回文，英文 palindrome，如果该字符串的反转与原始字符串相同，则该字符串称为回文字符串。

比如:

• radar
• level
• Able was I ere I saw Elba

反转字符串与原字符串比较

反转字符串或数字，并将反转的字符串或数字与原始值进行比较。

package com.yuzhou1su.RelearnJava.Util;

public class palindrome {

public static void main(String[] args) {

String str = "level", reverseStr = "";

int strLength = str.length();

for (int i = (strLength - 1); i >=0; --i) {
reverseStr = reverseStr + str.charAt(i);
}

if (str.toLowerCase().equals(reverseStr.toLowerCase())) {
System.out.println(str + " is a Palindrome String.");
}
else {
System.out.println(str + " is not a Palindrome String.");
}
}
}

输出结果：​​level is a Palindrome String.​​

双指针

先把字符串转换为字符串数组，然后分别从字符串分组的前后进行遍历字符串，前后对比。

package com.yuzhou1su.RelearnJava.Util;

public class palindrome {

public static void main(String[] args) {

String str = "level";
char[] strArray = str.toCharArray();

if (isPalindrom(strArray)) {
System.out.println(str + " is a Palindrome String.");
} else {
System.out.println(str + " is not a Palindrome String.");
}
}

public static boolean isPalindrom(char[] word){
int i1 = 0;
int i2 = word.length - 1;
while (i2 > i1) {
if (word[i1] != word[i2]) {
return false;
}
++i1;
--i2;
}
return true;
}
}

Python中讨巧解法

def isPalindrome(self, x: int) -> bool:
return str(x)==str(x)[::-1]