Hey I need help fixing this error. It says out of range. Any help wiil be highly appreciated.

C++ program to add hexadecimal numbers. Other functions cannot be added, and it SHOULD NOT t be changed into decimal, perform the addiditon and convert back to hexadecimal

#include #include #include

// NOTE: The ONLY files that should be #included for this assignment are iostream, vector, and string // No other files should be #included

using namespace std;

string addhex(string, string);

int main()

{

cout << "hexadecimal A4 + A5 = " << addhex("A4", "A5") << endl; //you should get 149

cout << "hexadecimal 2B + C = " << addhex("2B", "C") << endl; //you should get 37

cout << "hexadecimal FABC + 789 = " << addhex("FABC", "789") << endl; //you should get 10245

cout << "hexadecimal FFFFFF + FF = " << addhex("FFFFFF", "FF") << endl << endl; //you should get 10000FE

system("PAUSE");

return 0;

}

string addhex(string hex1, string hex2)

{

string result;

int sum = 0;

bool carry = false;

while (hex1.size() != hex2.size())

{

if (hex1.size() > hex2.size())

{

hex2.insert(0, "0");

}

else

{

hex1.insert(0, "0");

}

}

for (int i = hex1.size(); i >= 0; i--)

{

if (hex1.at(i) >= 0 && hex1.at(i) < 10)

{

sum += hex1.at(i) - '0';

}

else

{

sum += hex1.at(i) - 'A' + 10;

}

if (hex2.at(i) >= 0 && hex2.at(i) < 10)

{

sum += hex2.at(i) - '0';

}

else

{

sum += hex2.at(i) - 'A' + 10;

}

sum += (1 * carry);

carry = (sum >= 16);

sum = sum % 16;

if (sum <= 9)

{

result += '0' + sum;

}

else

{

result += 'A' + (sum - 10);

}

}

carry ? result += '1' : result = result;

return string(result.rbegin(), result.rend());

}