---

1. 求1+2+3+…+n

求1+2+3+…+n，要求不能使用乘除法、for、while、if、else、switch、case等关键字及条件判断语句（A?B:C）。

数据范围: 0 < n <= 200

class func{
public:
    static int i;
    static int sum;
    func(){
        sum+=i;
        ++i;
    }
};

int func::i = 1;
int func::sum = 0;

class Solution {
public:
    int Sum_Solution(int n) {
        func* p = new func[n];
        return func::sum;
    }
};

2. 计算是这一年的第几天

根据输入的日期，计算是这一年的第几天。

保证年份为4位数且日期合法。

#include <iostream>
using namespace std;

class Date{
public:
    int year;
    int month;
    int day;
    Date(){};
    
 	// 声明友元
    friend istream& operator>>(istream& in, Date& d);
	
    // 判断闰年
    bool isLeapYear(int year) const{
        return((year % 4 == 0 && year % 100 != 0) || year % 400 == 0);
    }
	
    // 获得日期
    int Getday(int year, int month) const{
        static const int Getdays[] =  {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
        if(month == 2 && isLeapYear(year))
            return 29;
        return Getdays[month - 1];
    }
	
    // 计算是这一年的第几天
    int my_sum(int year, int month, int day) const{
        int sum = 0;
        for(int i = 1;i < month; ++i){
            sum += Getday(year, i); 
        }
        sum += day;
        return sum;
    }
};

// >> 操作符重载
istream& operator>>(istream& in, Date& d){
    in >> d.year >> d.month >> d.day;
    return in;
}

int main()
{
    Date d;
    while(cin >> d){
        cout << d.my_sum(d.year, d.month, d.day) << endl;
    }
    return 0;
}

3. 求两个日期之间的天数

有两个日期，求两个日期之间的天数，如果两个日期是连续的我们规定他们之间的天数为两天

#include <bits/stdc++.h>
using namespace std;
int day[13]={0,31,28,31,30,31,30,31,31,30,31,30,31};
int leap(int year){
	if((year%4==0 && year%100!=0) || year%400==0) return 1;
	return 0;
}

int main(){
	int day1,day2,mon1,mon2,year1,year2;
	scanf("%4d%2d%2d",&year1,&mon1,&day1);
	scanf("%4d%2d%2d",&year2,&mon2,&day2);

	int sum1=0,sum2=0;
	for(int yy=0;yy<year1;yy++){
		if(leap(yy)) sum1+=366;
		else sum1+=365;
	} 
	if(leap(year1)) day[2]=29;
		else day[2]=28;
	for(int mm=1;mm<mon1;mm++){
		sum1+=day[mm];
	}
	sum1+=day1;
	
	for(int yy=0;yy<year2;yy++){
		if(leap(yy)) sum2+=366;
		else sum2+=365;
	} 
	if(leap(year2)) day[2]=29;
		else day[2]=28;
	for(int mm=1;mm<mon2;mm++){
		sum2+=day[mm];
	}
	sum2+=day2;
	cout<<abs(sum1-sum2)+1<<endl;
	return 0;
}

4. 算出第n天是几月几号

给出年分m和一年中的第n天，算出第n天是几月几号。

#include <iostream>
using namespace std;

class Date {
  public:
    // 判断是否为闰年
    bool isLeapYear(int year) const {
        if ((year % 4 == 0 && year % 100 != 0) || year % 400 == 0)
            return true;
        return false;
    }

    // 获取某年某月的天数
    int GetMonthDay(int year, int month) const {
        static const int GetMonthDay[] = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
        if (month == 2 && isLeapYear(year))
            return 29;
        return GetMonthDay[month - 1];
    }

    // 构造函数
    Date(int year, int x) {
        this->year = year;
        if (x <= 31) {
            month = 1;
            day = x;
        } else {
            x -= 31;
            month = 2;
            for (int i = 2; x > GetMonthDay(year, i); ++i) {
                ++month;
                x -= GetMonthDay(year, i);
            }
                day = x;
        }  
    }


  private:
    int year;
    int month;
    int day;

    friend ostream& operator<<(ostream& out, const Date& d);
};

// << 运算符重载
ostream& operator<<(ostream& out, const Date& d) {
    if (d.month < 10 &&d.day < 10)   out << d.year << "-0" << d.month << "-0" << d.day << endl;
    else if (d.month < 10)   out << d.year << "-0" << d.month << "-" << d.day <<endl;
    else if (d.day < 10)   out << d.year << "-" << d.month << "-0" << d.day << endl;
    else   out << d.year << "-" << d.month << "-" << d.day << endl;
    return out;
}

int main() {
    int year, x;
    while (cin >> year >> x){
        Date d(year, x);
        cout << d;
    }

        return 0;
}

5. 计算一个日期加上若干天后是什么日期

设计一个程序能计算一个日期加上若干天后是什么日期。

#include <iostream>
using namespace std;

class Date {
public:
    // 判断是否为闰年
    bool isLeapYear(int year) const {
        if ((year % 4 == 0 && year % 100 != 0) || year % 400 == 0)
            return true;
        return false;
    }

    // 获取某年某月的天数
    int GetMonthDay(int year, int month) const {
        static const int GetMonthDay[] = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
        if (month == 2 && isLeapYear(year))
            return 29;
        return GetMonthDay[month - 1];
    }

    // 日期天数递增一天
    void incrementDate() {
        ++day;
        if (day > GetMonthDay(year, month)) {
            day = 1;
            ++month;
            if (month > 12) {
                month = 1;
                ++year;
            }
        }
    }

// 后置++运算符重载
    Date& operator++(){
        Date tmp = *this;
        incrementDate();
        return *this;
    }

    Date(int year, int month, int day): year(year), month(month), day(day) {}


private:
    int year;
    int month;
    int day;

    friend ostream& operator<<(ostream& out, const Date& d);
};

// << 运算符重载
ostream& operator<<(ostream& out, const Date& d) {
    if (d.month < 10 && d.day < 10)   out << d.year << "-0" << d.month << "-0" << d.day << endl;
    else if (d.month < 10)   out << d.year << "-0" << d.month << "-" << d.day <<endl;
    else if (d.day < 10)   out << d.year << "-" << d.month << "-0" << d.day << endl;
    else   out << d.year << "-" << d.month << "-" << d.day << endl;
    return out;
}

int main() {
    int n;
    int y, m, d, x;
    cin >> n;
        for (int i = 0; i < n; ++i) {
            cin >> y >> m >> d >> x;
            Date d1(y, m, d);
            while(x--){
                ++d1;
            }
            cout << d1;
        }

    return 0;
}