Don`t know what to do. My prog passes all tests like
1992, 199999992, 1-digit numbers. It passes all teste I`ve seen on this forum. Please, tell me, what can be the problem. Thank you.

#include <stdio.h>
#include <conio.h>
#include <iostream>
#include <string>
using namespace std;
typedef long long ll;

string make_palindrome(string str)
{
    string palindrome = str;
    if (str.size() % 2 == 0)
    {
        int j = 0;
        for (int i = 0; i < str.size() / 2; i++,j++)
            palindrome[j] = str[i];
        for (int i = str.size() / 2 - 1; i >= 0; i--,j++)
            palindrome[j] = str[i];
    }
    else
    {
        int j = 0;
        for (int i = 0; i < str.size() / 2; i++,j++)
            palindrome[j] = str[i];
        for (int i = str.size() / 2; i >= 0; i--,j++)
            palindrome[j] = str[i];
    }
    return palindrome;
}

void add_1(string *str)
{

    int start = 0;
    if ((str->size() - 1) % 2 == 0)
        start = (str->size() - 1) / 2;
    else start = (str->size() - 1) / 2 + 1;
    for (int i = start; i >= 0; i--)
    {
        if ((*str)[i] + 1 < '9')
        {
            if ( i == start)(*str)[i]++;
            break;
        }
        else {
            (*str)[i] = '0';
            (*str)[i - 1]++;
        }
    }
}
void extract_1(string *str)
{
    int start = 0;
        if ((str->size() - 1) % 2 == 0)
            start = (str->size() - 1) / 2;
        else start = (str->size() - 1) / 2 + 1;
        for (int i = start; i >= 0; i--)
        {
            if ((*str)[i] - 1 >= '0')
            {
                (*str)[i]--;
                break;
            }
            else {
                (*str)[i] = '9';
            }
        }
}

int main(void)
{
    string in;
    cin >> in;
    string stemp = make_palindrome(in);
    string ans;
    if (in.size() == 1)
    {
        cout << in;
        return 0;
    }
    if (in.compare(stemp) == 1)
    {
        string str = '0' + in;
        add_1(&str);
        if (str[0] != '0')
            ans = make_palindrome(str);
        else {
            string temp = str;
            temp.erase(temp.begin());
            ans = make_palindrome(temp);
        }
    }
    else if (in.compare(stemp) == -1)
    {
        string str = '0' + in;
        extract_1(&str);
        if (str[0] != '0')
            ans = make_palindrome(str);
        else {
            string temp = str;
            temp.erase(temp.begin());
            ans = make_palindrome(temp);
        }
    }
    else
    {
        cout << in;
        return 0;
    }

    if (ans.compare(stemp) == 1)
    {
        cout << ans;
    }
    else if (ans.compare(stemp) == -1)
    {
        cout << stemp;
    }
    else cout << stemp;

    return 0;
}

Edited by author 20.10.2017 17:12

Input: 798.
Output: 1001.
Problem in add_1 function, changed < '9' on <= '9' got AC.

798
808