Why "compareBigInterger" return just =

This is what I have been working:

Giving 2 positive integer (at most 100 dight).

Compare that 2 integer .

Note: That 2 integer can contain leading zeros.(that means you have to remove zeros first)

Because 100 digits is too big so I use string

But in my program below,it just return '=' I debugged it and know the for loop doesn't working

Can anyone help? Thanks in avdance.

My code:

#include <iostream>
#include <string>

using namespace std; // I know this is bad but it's just a small program

char compareBigInterger(string str1,string str2)
{
    while (str1[0] != 0) str1.erase(0, 1);
    while (str2[0] != 0) str2.erase(0, 1);

    char answerHold {' '};
    if (str1.size() > str2.size())
    {
        answerHold = '>';
    }
    else if (str1.size() < str2.size())
    {
        answerHold = '<';
    }
    else
    {
        for (int i = 0; i < str1.size(); i++)
        {
            if (int(str1[i] - 48) < int(str2[i] - 48)) // 48 = '1' - 1
            {
                answerHold = '<';
                break;
            }
            else if (int(str1[i] - 48) > int(str2[i] - 48))
            {
                    answerHold = '>';
                    break;
            }
        }
    }
    if (answerHold == ' ')
            answerHold = '=';
    return answerHold;
}

int main()
{
    string str1;
    string str2;
    cin >> str1 >> str2;
    cout << char{compareBigInterger(str1, str2)};
}