布尔值不会在回文函数（C ++）中调整为false

Question

I've sadly read every post pertaining to this topic and can't seem to solve my issue. It's driving me mad.

For some reason on my second or third iteration, if (beg != end) won't return false. It returns false properly if I input, for instance, "bool", but not "blob."

I printed beg and end to make sure things are flowing properly, but still can't find where things are going wrong.

Thank you!!!

#include <iostream>
#include <string>
using namespace std;

bool palindrome_check (string str)
{
    string return_str;
    int length = str.length()-1;
    string beg = str.substr(0, 1);
    string end = str.substr(length, 1);

    if (beg != end)
    {
      //  cout << beg << " " << end << endl;
        return false;
    }

    else if ((str.length() > 2) && (str.length() != 0))
    {
        string new_str = str.substr(1, length - 1);
      //  cout << new_str << endl;
        palindrome_check(new_str);
    }
        return true;
}
int main ()
{

    string input;
    cout << "Enter a string: ";
    cin >> input;

    bool is_palindrome = palindrome_check (input);

    cout << is_palindrome << endl;
}

Answer 1

You should have used the return values of recursive calls:

        string new_str = str.substr(1, length - 1);
        return palindrome_check(new_str);
    }
    return true;

And you should have checked the length of the input string before you extract the first and the last character from it.

If you fix the two mistakes, it should be alright then.