关于高精度的那些事 ~

近不知道哪根筋抽风居然想起写高精度，确实很恶心。。。

不过有一点好处是以后碰到高精度的恶心题就不用在写了。在网上找到的高精度模板基本只有 + - * / 4种运算，我的加上了个 % 。。。

Code:

#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;

const int LEN = 10001;

struct BigInt
{
    static const int BIT = 9;
    static const int MOD = 1000000000;//1eBIT

    long long s[LEN];
    bool flag;

    BigInt()
    {
        memset(s, 0, sizeof(s));
        flag = s[0] = 1;
    }

    void init()
    {
        memset(s, 0, sizeof(s));
        s[0] = 1;
    }

    BigInt operator = (const char *num)
    {
        int l = strlen(num);
        s[0] = 0;
        for(int i = l - 1; i >= 0; i -= BIT)
        {
            ++s[0];
            long long w = 1;
            for(int j = i; j > i - BIT && j >= 0; j--)
            {
                s[s[0]] += (num[j] ^ 48) * w;
                w = (w << 1) + (w << 3);
            }
        }
        return *this;
    }

    BigInt operator = (const int num)
    {
        char a[LEN];
        sprintf(a, "%d", num);
        *this = a;
        return *this;
    }

    BigInt(int num)
    {
        *this = num;
    }

    BigInt(const char *num)
    {
        *this = num;
    }

    BigInt operator + (const BigInt &a)
    {
        BigInt c;
        int x = 0;
        c.s[0] = max(a.s[0], s[0]) + 1;
        for(int i = 1; i <= c.s[0]; i++)
        {
            c.s[i] = a.s[i] + s[i] + x;
            x = c.s[i] / MOD;
            c.s[i] %= MOD;
        }
        while(c.s[c.s[0]] == 0 && c.s[0] > 1) c.s[0]--;
        return c;
    }

    BigInt operator += (const BigInt &a)
    {
        *this = *this + a;
        return *this;
    }

    bool operator == (const BigInt &a)
    {
        int up = max(s[0], a.s[0]);
        for(int i = 0; i < up; i++)
            if(s[up - i] != a.s[up - i]) return false;
        return true;
    }

    bool operator > (const BigInt &a)
    {
        if(s[0] != a.s[0]) return s[0] > a.s[0];
        int up = max(s[0], a.s[0]);
        for(int i = 0; i < up; i++)
            if(s[up - i] != a.s[up - i]) return s[up - i] > a.s[up - i];
        return false;
    }

    bool operator < (const BigInt &a)
    {
        if(s[0] != a.s[0]) return s[0] < a.s[0];
        int up = max(s[0], a.s[0]);
        for(int i = 0; i < up; i++)
            if(s[up - i] != a.s[up - i]) return s[up - i] < a.s[up - i];
        return false;
    }

    bool operator >= (const BigInt &a)
    {
        if(*this > a || *this == a) return true;
        return false;
    }

    bool operator <= (const BigInt &a)
    {
        if(*this < a || *this == a) return true;
        return false;
    }

    BigInt operator - (const BigInt &a)
    {
        BigInt c;
        c.s[0] = max(a.s[0], s[0]) + 1;
        if(*this < a) c.flag = false;
        for(int i = 1; i <= c.s[0]; i++)
        {
            if(c.flag) c.s[i] += s[i] - a.s[i];
            else c.s[i] += a.s[i] - s[i];
            if(c.s[i] < 0)
            {
                c.s[i] += MOD;
                c.s[i + 1]--;
            }
        }
        while(c.s[c.s[0]] == 0 && c.s[0] > 1) c.s[0]--;
        return c;
    }

    BigInt operator -= (const BigInt &a)
    {
        *this = *this - a;
        return *this;
    }

    BigInt operator * (const BigInt &a)
    {
        BigInt c;
        c.s[0] = s[0] + a.s[0];
        for(int i = 1; i <= s[0]; i++)
        {
            int x = 0;
            for(int j = 1; j <= a.s[0]; j++)
            {
                c.s[i + j - 1] += s[i] * a.s[j] + x;
                x = c.s[i + j - 1] / MOD;
                c.s[i + j - 1] %= MOD;
            }
            c.s[i + a.s[0]] = x;
        }
        while(c.s[c.s[0]] > 0) c.s[0]++;
        while(c.s[c.s[0]] == 0 && c.s[0] > 1) c.s[0]--;
        return c;
    }

    BigInt operator *= (const BigInt &a)
    {
        *this = *this * a;
        return *this;
    }

    BigInt operator << (const int &num)
    {
        s[0]++;
        for(int i = 1; i <= s[0]; i++)
        {
            s[i] <<= num;
            if(s[i - 1] >= MOD)
                s[i - 1] -= MOD, ++s[i];
        }
        while(s[s[0]] == 0 && s[0] > 1) s[0]--;
        return *this;
    }

    BigInt operator >> (const int &num)
    {
        for(int i = s[0]; i >= 1; i--)
        {
            if((s[i] & 1) && i > 1) s[i - 1] += MOD;
            s[i] >>= num;
        }
        while(s[s[0]] == 0 && s[0] > 1) s[0]--;
        return *this;
    }

    BigInt operator / (const BigInt &k)
    {
        BigInt c = *this, tmp, lt, a;
        a = k;
        tmp.s[1] = 1;
        while(c >= a)
        {
            a = a << 1;
            tmp = tmp << 1;
        }
        while(tmp.s[0] > 1 || tmp.s[1])
        {
            if(c >= a)
            {
                c -= a;
                lt += tmp;
            }
            a = a >> 1;
            tmp = tmp >> 1;
        }
        c = lt;
        while(c.s[c.s[0]] == 0 && c.s[0] > 1) c.s[0]--;
        if(c.s[0] < 1) c.s[c.s[0] = 1] = 0;
        return c;
    }

    BigInt operator /= (const BigInt &a)
    {
        *this = *this / a;
        return *this;
    }

    BigInt operator % (const BigInt &a)
    {
    	BigInt zero=0,tmp=a;
    	if(tmp==zero)
    		return zero;
        BigInt d = *this, 
		c = *this / a;
        c *= a;
        return d - c;
    }

    BigInt operator %= (const BigInt &a)
    {
        *this = *this % a;
        return *this;
    }

}a,b;


ostream& operator << (ostream &out, const BigInt &a)
{
    if(!a.flag) putchar('-');
    printf("%d", a.s[a.s[0]]);
    for(int i = a.s[0] - 1; i >= 1; i--)
        printf("%09d", a.s[i]);
    return out;
}

istream& operator >> (istream &in, BigInt &a)
{
    char str[LEN];
    in >> str;
    a = str;
    return in;
}

int main()
{
    cin >> a >> b;
    cout << a + b << endl;
    cout << a - b << endl;
    cout << a * b << endl;
    cout << a / b << endl;
    cout << a % b << endl;
    return 0;
}

放在这里，主要是备忘以及需要的时候拿出来用。