大数模板！

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#define UNIT 10

using namespace std;

struct Bignum
{
    int val[105];
    int len;

    Bignum ()
    {
        memset (val, 0, sizeof(val));
        len = 1;
    }

    Bignum operator = (const int &a)
    {
        int t, p = a;
        len = 0;
        while (p >= UNIT)
        {
            t = p - (p/UNIT)*UNIT;
            p = p / UNIT;
            val[len++] = t;
        }
        val[len++] = p;
        return *this;
    }

    Bignum operator + (const Bignum &a) const//大数加大数
    {
        Bignum x = a;
        int L;
        L = a.len > len ? a.len : len;
        for (int i = 0; i < L; ++i)
        {
            x.val[i] += val[i];
            if (x.val[i] >= UNIT)
            {
                x.val[i+1]++;
                x.val[i] -= UNIT;
            }
        }
        if (x.val[L] != 0)
            x.len = L+1;
        else
            x.len = L;
        return x;
    }

    Bignum operator - (const Bignum &a) const
    {
        bool flag;
        Bignum x1, x2;
        if (*this > a)
        {
            x1 = *this;
            x2 = a;
            flag = 0;
        }
        else
        {
            x1 = a;
            x2 = *this;
            flag = 1;
        }
        int j, L = x1.len;
        for (int i = 0; i < L; ++i)
        {
            if (x1.val[i] < x2.val[i])
            {
                j = i+1;
                while (x1.val[j] == 0)
                    j++;
                x1.val[j--]--;
                while (j > i)
                    x1.val[j--] += UNIT-1;
                x1.val[i] += UNIT-x2.val[i];
            }
            else
                x1.val[i] -= x2.val[i];
        }
        while (x1.val[x1.len-1] == 0 && x1.len > 1)
            x1.len--;
        if (flag)
            x1.val[x1.len-1] = -x1.val[x1.len-1];
        return x1;
    }

    Bignum operator * (const Bignum &a) const//大数乘大数
    {
        Bignum x;
        int i, j, up;
        int x1, x2;
        for (i = 0; i < len; i++)
        {
            up = 0;
            for (j = 0; j < a.len; j++)
            {
                x1 = val[i]*a.val[j] + x.val[i+j] + up;
                if (x1 >= UNIT)
                {
                    x2 = x1 - x1/UNIT*UNIT;
                    up = x1 / UNIT;
                    x.val[i+j] = x2;
                }
                else
                {
                    up = 0;
                    x.val[i+j] = x1;
                }
            }
            if (up != 0)
                x.val[i+j] = up;
        }
        x.len = i + j;
        while (x.val[x.len-1] == 0 && x.len > 1)
            x.len--;
        return x;
    }

    Bignum operator / (const int &a) const//大数除小数
    {
        Bignum x;
        int down = 0;
        for (int i = len-1; i >= 0; --i)
        {
            x.val[i] = (val[i]+down*UNIT) / a;
            down = val[i] + down*UNIT - x.val[i]*a;
        }
        x.len = len;
        while (x.val[x.len-1] == 0 && x.len > 1)
            x.len--;
        return x;
    }

    int operator % (const int &a) const//大数模小数
    {
        int x = 0;
        for (int i = len-1; i >= 0; --i)
            x = ((x*UNIT)%a+val[i]) % a;
        return x;
    }

    Bignum operator ^ (const int &a) const
    {
        Bignum p, x;
        x.val[0] = 1;
        if(a < 0)
            exit(-1);
        if(a == 0)
            return x;
        if(a == 1)
            return *this;
        int n = a, i;
        while(n > 1)
        {
            p = *this;
            for(i = 1; (i<<1) <= n; i<<=1)
                p = p * p;
            n -= i;
            x = x * p;
            if(n == 1)
                x = x * (*this);
        }
        return x;
    }

    bool operator > (const Bignum &a) const
    {
        int now;
        if (len > a.len)
            return true;
        else if (len == a.len)
        {
            now = len - 1;
            while (val[now] == a.val[now] && now >= 0)
                now--;
            if(now >= 0 && val[now] > a.val[now])
                return true;
            else
                return false;
        }
        else
            return false;
    }
};

int main()
{
    /*f[0] = 1;
    for(int i=1;i<=100;i++)
    f[i]=f[i-1]*(4*i-2)/(i+1);//卡特兰数递推式
    int n;
    while(scanf("%d",&n)==1)
    {
        if(n==-1)
            break;
        f[n].print();
    }*/
    return 0;
}