P106 高精度整数部分

大数模板

#include<bits/stdc++.h>
#define deb(x) cerr<<#x<<" = "<<(x)<<'\n';
using namespace std;
typedef long long ll;

//大整数
struct BigInteger
{
    static const int BASE = 100000000;//和WIDTH保持一致
    static const int WIDTH = 8;//八位一存储,如修改记得修改输出中的%08d
    bool sign;//符号, 0表示负数
    size_t length;
    vector<int> num;//反序存
//构造函数
    BigInteger (long long x = 0) { *this = x; }
    BigInteger (const string& x) { *this = x; }
    BigInteger (const BigInteger& x) { *this = x; }
//剪掉前导0
    void cutLeadingZero(){
        while(num.back() == 0 && num.size() != 1) { num.pop_back(); }
    }
//设置数的长度
    void setLength(){
        cutLeadingZero();
        int tmp = num.back();
        if(tmp == 0) { length = 1; }
        else{
            length = (num.size() - 1) * WIDTH;
            while(tmp > 0) { ++length; tmp /= 10; }
        }
    }
//赋值运算符
    BigInteger& operator = (long long x)
    {
        num.clear();
        if (x >= 0) sign = true;
        else { sign = false; x = -x; }
        do
        {
            num.push_back(x%BASE);
            x/=BASE;
        } while(x>0);
        setLength();
        return *this;
    }
//赋值运算符
    BigInteger& operator = (const string& str)
    {
        num.clear();
        sign = (str[0] != '-');//设置符号
        int x, len=(str.size()-1-(!sign))/WIDTH+1;
        for(int i=0;i<len;i++)
        {
            int End=str.length()-i*WIDTH;
            int start=max((int)(!sign), End-WIDTH);//防止越界
            sscanf(str.substr(start,End-start).c_str(),"%d",&x);
            num.push_back(x);
        }
        setLength();
        return *this;
    }
//赋值运算符
    BigInteger& operator = (const BigInteger& tmp)
    {
        num = tmp.num;
        sign = tmp.sign;
        length = tmp.length;
        return *this;
    }
//将该大数变为一个字符串 
    string tostring()
    {
        string ans = "";
        for (int i = 0; i < num.size(); i++)
            ans.insert(0, to_string(num[i]));
        if (!sign) ans.insert(0, "-");//负数 
        return ans;
    }
//数的位数
    size_t size() const { return length; }
//*10^n 除法中用到
    BigInteger e(size_t n) const
    {
        int tmp = n % WIDTH;
        BigInteger ans;
        ans.length = n + 1;
        n /= WIDTH;
        while (ans.num.size() <= n) ans.num.push_back(0);
        ans.num[n] = 1;
        while (tmp--) ans.num[n] *= 10;
        return ans*(*this);
    }
//绝对值
    BigInteger abs() const
    {
        BigInteger ans(*this);
        ans.sign = true;
        return ans;
    }
//正号
    const BigInteger& operator + () const { return *this; }
// + 运算符
    BigInteger operator + (const BigInteger& b) const
    {
        if (!b.sign) { return *this - (-b); }
        if (!sign) { return b - (-*this); }
        BigInteger ans;
        ans.num.clear();
        for(int i=0,g=0;;i++)
        {
            if(g==0&&i>=num.size()&&i>=b.num.size()) break;
            int x=g;
            if(i<num.size()) x+=num[i];
            if(i<b.num.size()) x+=b.num[i];
            ans.num.push_back(x%BASE);
            g=x/BASE;
        }
        ans.setLength();
        return ans;
    }
//负号
    BigInteger operator - () const
    {
        BigInteger ans(*this);
        if (ans != 0) ans.sign = !ans.sign;
        return ans;
    }
// - 运算符
    BigInteger operator - (const BigInteger& b) const
    {
        if (!b.sign) { return *this + (-b); }
        if (!sign) { return -((-*this) + b); }
        if (*this < b) { return -(b - *this); }
        BigInteger ans;
        ans.num.clear();
        for(int i=0,g=0;;i++)
        {
            if(g==0&&i>=num.size()&&i>=b.num.size()) break;
            int x=g; g=0;
            if(i<num.size()) x+=num[i];
              if(i<b.num.size()) x-=b.num[i];
              if(x<0){
                x+=BASE;g=-1;
              }
              ans.num.push_back(x);
        }
        ans.setLength();
        return ans;
    }
// * 运算符
    BigInteger operator * (const BigInteger& b) const
    {
        int lena = num.size(), lenb = b.num.size();
        vector<long long> ansLL;
        for (int i = 0; i < lena+lenb; i++) ansLL.push_back(0);
        for (int i = 0; i < lena; i++){
            for (int j = 0; j < lenb; j++){
                ansLL[i+j] += (long long)num[i]*(long long)b.num[j];
            }
        }
        while (ansLL.back() == 0 && ansLL.size() != 1) ansLL.pop_back();
        int len = ansLL.size();
        long long g = 0, tmp;
        BigInteger ans;
        ans.sign = (ansLL.size() == 1 && ansLL[0] == 0) || (sign == b.sign);
        ans.num.clear();
        for (int i = 0; i < len; i++)
        {
            tmp = ansLL[i];
            ans.num.push_back((tmp + g)%BASE);
            g = (tmp + g) / BASE;
        }
        if (g > 0) ans.num.push_back(g);
        ans.setLength();
        return ans;
    }
// / 运算符 (大数除小数)
    BigInteger operator / (const long long& b) const
    {
        BigInteger c;
        c.num.clear();
        for(int i=0;i<num.size();i++){
            c.num.push_back(0);
        }
        long long g=0;
        for(int i=num.size()-1;i>=0;i--)
        {
            c.num[i]=(num[i]+g*BASE)/b;
               g=num[i]+g*BASE-c.num[i]*b;
        }
        for(int i=num.size()-1;c.num[i]==0;i--){
            c.num.pop_back();
        }
        return c;
    }
// /运算符 (大数除大数)
    BigInteger operator / (const BigInteger& b)    const
    {
        BigInteger aa((*this).abs());
        BigInteger bb(b.abs());
        if (aa < bb) return 0;
        char *str = new char[aa.size() + 1];
        memset(str, 0, sizeof(char)*(aa.size()+1));
        BigInteger tmp;
        int lena = aa.length, lenb = bb.length;
        for (int i = 0; i <= lena - lenb; i++)
        {
            tmp = bb.e(lena - lenb - i);
            while (aa >= tmp)
            {
                ++str[i];
                aa = aa - tmp;
            }
            str[i] += '0';
        }
        BigInteger ans(str);
        delete[]str;
        ans.sign = (ans == 0 || sign == b.sign);
        return ans;
    }
// % 运算符 (大数取模小数)
    BigInteger operator % (const long long& b) const
    {
        long long ans=0,lena=num.size();
        for(int i=lena-1;i>=0;i--){
            ans = (ans*BASE+num[i])%b;
        }
        return ans;
    }
// %运算符 (大数取模大数)
    BigInteger operator % (const BigInteger& b)    const{
        return *this - *this / b * b;
    }

    BigInteger& operator ++ () { *this=*this+1;return *this; } // ++ 运算符
    BigInteger& operator -- () { *this=*this-1;return *this; } // -- 运算符
    BigInteger& operator += (const BigInteger& b) { *this=*this+b;return *this; } // += 运算符
    BigInteger& operator -= (const BigInteger& b) { *this=*this-b;return *this; } // -= 运算符
    BigInteger& operator *= (const BigInteger& b) { *this=*this*b;return *this; } // *=运算符
    BigInteger& operator /= (const long long& b)  { *this=*this/b;return *this; } // /=运算符
    BigInteger& operator /= (const BigInteger& b) { *this=*this/b;return *this; } // /= 运算符
    BigInteger& operator %= (const long long& b)  { *this=*this%b;return *this; } // %=运算符
    BigInteger& operator %= (const BigInteger& b) { *this=*this%b;return *this; } // %=运算符
// < 运算符
    bool operator < (const BigInteger& b) const
    {
        if (sign && !b.sign) { return false; }//正负
        else if(!sign && b.sign) { return true; }//负正
        else if(!sign && !b.sign) { return -b < -*this; }//负负
        //正正
        if(num.size()!=b.num.size()) return num.size()<b.num.size();
        for(int i=num.size()-1;i>=0;i--)
            if(num[i]!=b.num[i]) return num[i]<b.num[i];
        return false;
    }

    bool operator >  (const BigInteger& b) const { return b<*this; }              // >  运算符
    bool operator <= (const BigInteger& b) const { return !(b<*this); }           // <= 运算符
    bool operator >= (const BigInteger& b) const { return !(*this<b); }           // >= 运算符
    bool operator != (const BigInteger& b) const { return b<*this||*this<b; }     // != 运算符
    bool operator == (const BigInteger& b) const { return !(b<*this)&&!(*this<b); }//==运算符

    bool operator || (const BigInteger& b) const { return *this != 0 || b != 0; } // || 运算符
    bool operator && (const BigInteger& b) const { return *this != 0 && b != 0; } // && 运算符
    bool operator !  () { return (bool)(*this == 0); }                            // ！ 运算符

    //重载<<使得可以直接输出大数
    friend ostream& operator << (ostream &out,const BigInteger &x)
    {
        if (!x.sign) out<<'-';
        out<<x.num.back();
        for(int i=x.num.size()-2;i>=0;i--)
        {
            char buf[10];
            //如WIDTH和BASR有变化,此处要修改为%0(WIDTH)d
            sprintf(buf,"%08d",x.num[i]);
            for(int j=0;j<strlen(buf);j++) out<<buf[j];
        }
        return out;
    }
    //重载>>使得可以直接输入大数
    friend istream& operator >> (istream &in, BigInteger &x)
    {
        string str;
        in >> str;
        size_t len = str.size();
        int i, start = 0;
        if (str[0] == '-') start = 1;
        if (str[start] == '\0') return in;
        for (int i = start; i < len; i++){
            if (str[i] < '0' || str[i] > '9') return in;
        }
        x.sign = !start;
        x = str.c_str();
        return in;
    }
} ;

int main(){
    int n;
    while(cin >> n){
        //BigInteger ans = 1;
        BigInteger ans(1); //最好写成这样
        for(int i = 1; i < n+1; i++){
            //ans = ans * i;
            ans = ans * BigInteger(i);
        }
        cout << ans << endl;
    }
    return 0;
}