Solucion Gaston 2.0 C

#ifndef BIGNUMBER_H_INCLUDED
#define BIGNUMBER_H_INCLUDED

#include <iostream>
#include <algorithm>
#include <string.h>

using namespace std;

class BigNumber
{
private:
    string n;
public:
    BigNumber(string _n); ///Constructor
    string toStr(); ///Devolver string
    BigNumber operator*(BigNumber &b); ///Operador multiplicar
};

BigNumber::BigNumber(string _n)
{
    this->n = _n;
}

string BigNumber::toStr()
{
    return this->n;
}

BigNumber BigNumber::operator*(BigNumber &num)
{
    string sa = this->toStr();
    string sb = num.toStr();
    char *a = (char*)sa.c_str();
    char *b = (char*)sb.c_str();
    int t1 = sa.size(), t2 = sb.size();
    int tam = t1+t2+1; ///+1 changui
    int res[tam], p, i, j;

    for(i=0; i<tam; i++)
        res[i] = 0;

    for(i=0; i<t1/2; i++)
    {
        swap(a[i], a[t1-1-i]);
        swap(b[i], b[t2-1-i]);
    }

    for(i=0; i<t1; i++)
    {
        for(j=0; j<t2; j++)
        {
            p = (a[i]-'0')*(b[j]-'0');
            res[i+j] += p;
        }
    }

    for(i=0; i<tam-1; i++)
    {
        if(res[i] > 9)
        {
            res[i+1] += res[i]/10;
            res[i] %= 10;
        }
    }

    int maxPos = tam-1;
    while(maxPos >= 0 && res[maxPos] == 0)
        maxPos--;

    char r[maxPos+2];
    for(i=maxPos; i>=0; i--)
        r[maxPos-i] = (res[i]+'0');
    r[maxPos+1] = 0;

    return string(r);
}

ostream &operator<<(ostream &out, BigNumber &num)
{
    return out << num.toStr();
}

#endif // BIGNUMBER_H_INCLUDED