def fac(x):
    if len(x)==0 or len(x)==1:
        return "YES"
    if x[0]!=x[len(x)-1]:
        return "NO"
    return fac(x[1:len(x)-1])
s=input()
print(fac(s))

C++

从中间往两边判断。

int main(){
    string a; 
    int len; 
    cin >> a;
    len = a.length(); 
    for (int i = 0; i < len / 2; i++ ) { 
        if (a[i] != a[len - i - 1]) {
            cout << "NO"; 
            return 0;
        }
    }
    cout << "YES";
    return 0;
}

s = input()
if s == s[::-1]:
    print("YES")
else:
    print("NO")