Validate palindrome string

---

title: Verify the palindrome string
date: 2022-04-25 14:21:32
categories: LeetCode
tags: Make a little progress every day

---

subject

Verify the palindrome string

difficulty Simple

Given a string , Verify that it is a palindrome string , Consider only alphabetic and numeric characters , The case of letters can be ignored .

explain ： In this question , We define an empty string as a valid palindrome string .

Example 1:

Input : “A man, a plan, a canal: Panama”
Output : true
explain ：“amanaplanacanalpanama” It's a palindrome string

Example 2:

Input : “race a car”
Output : false
explain ：“raceacar” It's not a palindrome string

Tips ：1 <= s.length <= 2 * 105
character string s from ASCII Character composition

Code ：

class Solution {    public boolean isPalindrome(String s) {        // Convert all to lowercase first         s = s.toLowerCase();        StringBuilder sCopy = new StringBuilder();        for (int i = 0; i < s.length(); i++) {            // Self retaining letters and numbers             if(Character.isLetterOrDigit(s.charAt(i))) {                sCopy.append(s.charAt(i));            }        }        // Reverse string         StringBuffer sCopy2 = new StringBuffer(sCopy).reverse();        // Compare         return sCopy.toString().equals(sCopy2.toString());    }}

C++ edition ：

#include<bits/stdc++.h>using namespace std;class Solution {public:    bool isPalindrome(string s) {        string str;        for(char ch : s){            //  Consider only alphabetic and numeric characters             if(isalnum(ch)){                //  Convert characters to lowercase                 str += tolower(ch);            }        }        /** * c.rbegin()  Returns an inverse iterator , It points to the container c Last element of  * c.rend()  Returns an inverse iterator , It points to the container c The position in front of the first element of  */        string str2(str.rbegin(), str.rend());        //  Judge whether it is a palindrome string         return str == str2;    }};int main() {    Solution s;    cout << (s.isPalindrome("A man, a plan, a canal: Panama") ?"true":"false")<< endl;    return 0;}

The above is to verify the whole content of the palindrome string

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