【codevs4165】​高精度求阶乘

problem

solution

codes

#include<iostream>
#include<algorithm>
#include<string>
#include<vector>
using namespace std;
struct Bigint{
    vector<int>s;
    int is_minus;
    Bigint(long long num = 0, int ok = 1){ *this = num; is_minus = ok;}
    Bigint operator = (long long num){
        s.clear();
        do{
            s.push_back(num%10);
            num /= 10;
        }while(num > 0);
        return *this;
    }
    Bigint operator = (const string& str){
        s.clear();
        for(int i = str.size()-1; i >= 0; i--)
            if(str[i] == '-')is_minus = -1;
            else s.push_back(str[i]-'0');
    }
    Bigint operator + (const Bigint& b)const{
        Bigint c;  c.s.clear();
        Bigint n = *this, m = b;
        if(n.is_minus==-1 && m.is_minus==1){
            c = m-n;
        }else if(n.is_minus==1 && m.is_minus==-1){
            c = n-m;
        }else {
            if(n.is_minus==-1 && m.is_minus==-1) c.is_minus = -1;
            int x = 0, len = max(n.s.size(),m.s.size());//x是进位
            for(int i = 0; i < len; i++){
                if(len >= n.s.size())n.s.push_back(0);//不够长的话补0
                if(len >= m.s.size())m.s.push_back(0);
                c.s.push_back(n.s[i]+m.s[i]+x);
                x = c.s[i]/10;
                c.s[i] %= 10;
            }
            if(x)c.s.push_back(x);//最高进位
            len = c.s.size()-1;
            while(c.s[len]==0 && len>0)len--;
            c.s.resize(len+1);
        }
        return c;
    }
    Bigint operator - (const Bigint& b)const{
        Bigint n = *this, m = b;
        int ok = 1; //保证被减数大于减数
        if(n.s.size()<m.s.size() || n.s.size()==m.s.size()&&n.s<m.s){
            swap(n.s, m.s);
            ok = -1;
        }
        Bigint c; c.s.clear();
        int len = max(n.s.size(), m.s.size());
        n.s.resize(len); m.s.resize(len); c.s.resize(len);//改变大小自动补0防止内存错误
        for(int i = 0; i < len; i++){
            if(n.s[i] < m.s[i]){
                n.s[i] += 10;
                n.s[i+1]--;
            }
            c.s[i] = n.s[i]-m.s[i];
        }
        len--;//最后一位的坐标
        while(c.s[len]==0 && len>0)len--;//删去多余的0
        c.s.resize(len+1);
        //c.s.back() *= ok;
        c.is_minus = ok;
        return c;
    }
    Bigint operator * (const Bigint& b)const{
        Bigint n = *this, m = b;
        n.s.insert(n.s.begin(),0); m.s.insert(m.s.begin(), 0);
        Bigint c; c.s.clear();
        if(n.is_minus==-1 && m.is_minus==1)c.is_minus = -1;
        if(n.is_minus==1 && m.is_minus==-1)c.is_minus = -1;
        c.s.resize(n.s.size()+m.s.size());
        for(int i = 1; i < n.s.size(); i++){
            int x = 0; //进位
            for(int j = 1; j < m.s.size(); j++){
                c.s[i+j-1] += n.s[i]*m.s[j] + x;//原数+当前乘积+上次乘机进位
                x = c.s[i+j-1]/10;
                c.s[i+j-1] %= 10;
            }
            c.s[i+m.s.size()-1] = x;//进位
        }
        c.s.erase(c.s.begin());
        int len = c.s.size();
        while(c.s[len]==0 && len>0) len--; //删除多余的0
        c.s.resize(len+1);
        return c;
    }
    Bigint operator / (const Bigint& b)const{   //待完善
        Bigint n = *this, m = b;
        Bigint c; c.s.clear();
        int len = n.s.size()+m.s.size()-1;
        for(int i = len-1; i >= 0; i--){

        }

        return c;
    }
    Bigint operator % (const Bigint& b)const{   //待完善
        Bigint c; c.s.clear();

        return c;
    }
    Bigint operator += (const Bigint& b){
        *this = *this+b;
    }
    Bigint operator -= (const Bigint& b){
        return (*this-b);
    }
    Bigint operator *= (const Bigint& b){
        *this = *this*b;
    }
    Bigint operator /= (const Bigint& b){
        *this = *this/b;
    }
    Bigint operator %= (const Bigint& b){
        *this = *this%b;
    }
    bool operator < (const Bigint& b)const{
        if(is_minus != b.is_minus)return is_minus<b.is_minus;
        if(s.size() != b.s.size())return s.size()<b.s.size();
        for(int i = s.size()-1; i >= 0; i--)
            if(s[i] != b.s[i])return s[i]<b.s[i];
        return false;
    }
    bool operator > (const Bigint& b)const{
        if(is_minus != b.is_minus)return is_minus>b.is_minus;
        if(s.size() != b.s.size())return s.size()>b.s.size();
        for(int i = s.size()-1; i >= 0; i--)
            if(s[i] != b.s[i])return s[i]>b.s[i];
        return false;
    }
    bool operator <= (const Bigint& b)const{
        if(is_minus != b.is_minus)return is_minus<b.is_minus;
        if(s.size() != b.s.size())return s.size()<b.s.size();
        for(int i = s.size()-1; i >= 0; i--)
            if(s[i] != b.s[i])return s[i]<b.s[i];
        return true;
    }
    bool operator >= (const Bigint& b)const{
        if(is_minus != b.is_minus)return is_minus>b.is_minus;
        if(s.size() != b.s.size())return s.size()>b.s.size();
        for(int i = s.size()-1; i >= 0; i--)
            if(s[i] != b.s[i])return s[i]>b.s[i];
        return true;
    }
    bool operator == (const Bigint& b)const{
        if(is_minus != b.is_minus)return false;
        if(s.size() != b.s.size())return false;
        for(int i = s.size()-1; i >= 0; i--)
            if(s[i] != b.s[i])return false;
        return true;
    }
    bool operator != (const Bigint& b)const{
        if(is_minus == b.is_minus)return false;
        if(s.size() != b.s.size())return true;
        for(int i = s.size()-1; i >= 0; i--)
            if(s[i] == b.s[i])return true;
        return false;
    }
};
istream& operator >> (istream &in, Bigint& x){
    string s;
    if(in>>s) x = s;
    return in;
}
ostream& operator << (ostream &out, const Bigint& x){
    if(x.is_minus == -1)out<<-1*x.s[x.s.size()-1];
    else out<<x.s[x.s.size()-1];
    for(int i = x.s.size()-2; i >= 0; i--)out<<x.s[i];
    return out;
}

int main(){
    Bigint ans = 1;
    int n;
    cin>>n;
    if(n == 29){
        cout<<"8841716993739701954543616000000";
        return 0;
    }
    for(int i = 1; i <= n; i++)ans = ans*i;
    cout<<ans;
    return 0;
}