Adding big numbers using pointers (c++) - c++

Question

i need help, the code below does not work as it returns nothing when i run it. I'm trying to add big number so large that the numbers won’t be able to be represented in the standard C++ integer data structures
mission.cpp
void Big2Add(const char * num1, const char * num2, char * result)
{
string a = num1;
string b = num2;
int min = (a.length() < b.length() ? a.length():b.length());
int max = (a.length() < b.length() ? b.length():a.length());
int *n1 = new int[max];
int *n2 = new int[max];
for (unsigned int i=0; i < a.length(); i++)
{
n1[i] = a.at(a.length() - 1 -i) - 48;
}
cout << a << endl;
for (unsigned int i=0; i < b.length(); i++)
{
n2[i] = b.at(b.length()-1 -i) - 48;
}
cout << b << endl;
int carry = 0;
int* sum = new int[max];
int k=0;
for (k = 0; k < max; k++)
{
sum[k] = (n1[k] + n2[k] + carry) % 10;
if ( (n1[k] + n2[k] + carry) >= 10)
carry = 1;
else carry = 0;
}
sum[max] = carry;
for (int j= max; j >= 0; j--)
{
*result = sum[j];
}
}
main.cpp
char result[10];
const char * num1 = "10";
const char * num2 = "10";
Big2Add(num1, num2, result);
cout << "Part 3" << endl;
cout << "The addition of " << num1 << " and " << num2 << " is " << result << endl;
cout << endl;

Answer 1

First obvious bug:
int* sum = new int[max];
...
sum[max] = carry;
You need to allocate max+1 in order to use position max.
Second and third obvious bugs:
*result = sum[j];
You forgot to advance result and you forgot to add '0'
Fourth, you forgot to null terminate the string.
Try:
for (int j= max; j >= 0; j--)
{
*(result++) = sum[j] + '0';
}
*result = 0;

Answer 2

ok it works now tks but my main problem now is that is that there is a extra zero in front of my answer if let say i do 10 plus 10 it will give me 010 or 100 with 10 it will give me 0110 but if i plus 99 with 99 it will give 198 y?
void Big2Add(const char * num1, const char * num2, char * result)
{
string a = num1;
string b = num2;
int max = (a.length() < b.length() ? b.length():a.length());
int *n1 = new int[max];
int *n2 = new int[max];
unsigned int i;
for (i=0; i < a.length(); i++)
{
n1[i] = a.at(a.length() - 1 -i) - 48;
}
for (int j = i; j < max; ++j)
{
n1[j] = 0;
}
for (i=0; i < b.length(); i++)
{
n2[i] = b.at(b.length()-1 -i) - 48;
}
for (int j = i; j < max; ++j)
{
n2[j] = 0;
}
int carry = 0;
int* sum = new int[max];
int k=0;
for (k = 0; k < max; k++)
{
sum[k] = (n1[k] + n2[k] + carry) % 10;
if ( (n1[k] + n2[k] + carry) >= 10)
carry = 1;
else carry = 0;
}
sum[max] = carry;
for (int j= max ; j >= 0; j--)
{
if(sum[0] == 0)
{
}
*(result++) = sum[j] + '0';
}
*result = 0;
}