a=input()
i=0
j=len(a)-1
while i<=j:
    if a[i]==a[j]:
        i+=1
        j-=1
    else:
        print('no')
        exit()
print('yes')

升级版回文串

#include <iostream>
#include <string>
#include <cmath>
using namespace std;
string PalindromicString(string str){//输入中文会有BUG
    int len=str.size();
    string res="yes";
        int half;
        if(len%2==0){
            half=len/2;
        }
    else{
            half=ceil(len/2);
    }
    for(int i=1;i<=half;i++){
        if(str[i-1]!=str[len-i]){//数组越界:(
            res="no";
                    break;
            }
    }
    return res;
}

int main(){
    string str,res;
    cin>>str;
    res=PalindromicString(str);
    cout<<res<<endl;
    return 0;
}

s=input()

n=len(s)
ishw='bala'
for i in range(n):
if(s[i]!=s[n-i-1]):
ishw='sss'

if ishw=='bala':
print("yes")
else:
print("no")

#include <stdio.h>
#include <cstring>
#include <iostream>
using namespace std;
string s;
int main()
{
cin>>s;
for(int i=0,j=s.length()-1;i<=j;i++,j--)
if(s[i]!=s[j])
{
cout<<"no";
return 0;
}
cout<<"yes";
return 0;
}

#include<bits/stdc++.h>
using namespace std;
int main()
{
string a;
cin>>a;
int c=a.length();
for(int i=0;i<c;i++)
if(a[i]!=a[c-i-1])
{
cout<<"no"<<endl;
return 0;
}
cout<<"yes"<<endl;
return 0;
}