[MATH]Big Integer +

#include <iostream>
#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <string>
using std::string;
using std::ostream;
using std::cout;
using std::cin;
using std::endl;
const int MAX = 220;
//#define online

class CHugeInt
{
private:
    bool positive;
    char s[MAX];
    /**
    /* 计算大小关系，使得交换顺序来便于计算
    ****/
    int Compare(const CHugeInt & c) const// < -1, == 0, > 1
    {
        int L1 = strlen(s);
        int L2 = strlen(c.s);
        if(L1 < L2)
            return -1;
        if(L1 > L2)
            return 1;
        // L1 == L2
        for(int i = 0; i < L1; i++)
        {
            if(s[i] < c.s[i])
                return -1;
            if(s[i] > c.s[i])
                return 1;
        }
        return 0;
    }
    /***
    /* 私有成员函数，专门计算 a + b，且满足a > b;
    ***/
    CHugeInt Add(const CHugeInt &a, const CHugeInt & b) const
    {
        CHugeInt tp(a);

        tp.positive = true;
        int L1 = strlen(tp.s);
        int L2 = strlen(b.s);
        int Forward = 0;
        for(int i = L1-1, j = L2 - 1; i>=0; --i, --j)
        {
            int _n1 = tp.s[i] - '0';
            int _n2 = 0;
            if(j >= 0)
                _n2 = b.s[j] - '0';
            int n = _n1 + _n2 + Forward;
            Forward = 0;
            if(n>=10)
            {
                Forward = 1;
                n -= 10;
            }
            tp.s[i] = n + '0';
        }
        if(Forward == 1)
        {
            for(int i = L1; i >=0 ; --i)
                tp.s[i+1] = tp.s[i];
            tp.s[0] = '1';
        }
        return tp;
    }
    /***
    /*专门计算 a - b的私有成员函数，且满足a >= b; 计算结果符号始终为正
    ****/
    CHugeInt Sub(const CHugeInt & a, const CHugeInt & b) const
    {
        CHugeInt tp(a);
        int L1 = strlen(tp.s);
        int L2 = strlen(b.s);
        int Forward = 0;
        for(int i = L1 - 1, j = L2 - 1; i>=0; i--,j--)
        {
            int _n1 = tp.s[i] - '0';
            int _n2 = 0;
            if(j >= 0) _n2 = b.s[j] - '0';
            int n = _n1 - _n2 - Forward;
            Forward = 0;
            if(n < 0)
            {
                Forward = 1;
                n += 10;
            }
            tp.s[i] = n + '0';
        }

        /**
        去掉大整数前面的首0，通过搬运数字
        **/
        if(tp.s[0] != '0')
            return tp;
        int non_zero_index = -1;// ȫΪ0
        for(int i = 0; i < L1; i++)
        {
            if(tp.s[i] != '0')
            {
                non_zero_index = i;
                break;
            }
        }
        if(non_zero_index == -1)
        {
            tp.s[1] = '