第三章：数据结构决定程序

#include<iostream>
#include<string>
#include<vector>
using namespace std;
int month[13] = {
0,    31,    28,    31,    30,    31,    30,    31,    31,    30,    31,    30,    31
//    1    2    3    4    5    6    7    8    9    10    11    12
};

class D{
public:
int year,mon,day;// 1900 <= year, 1 <= mon <= 12,
// 1 <= day <= 31
D(){}
D(int y, int m, int d):
year(y),mon(m),day(d){}

int yearday(void){//返回这一天是这一年的第几天
int sum = day;
for( int i = 1; i < mon; i++ )
sum += month[i];
if( isrun() && mon > 2 )
sum ++;
return sum;
}
bool isrun( void ){//是否是闰年
return (year%4==0&&year%100!=0)||(year%400==0);
}
};

int dist( D d1, D d2 ){//两个日期相差的天数
int sum = -(d1.yearday());
for( ; d1.year < d2.year ; d1.year++ )
sum += d1.isrun()?366:365;
return sum + d2.yearday();
}

int xingqiji( D d ){//某一天是星期几
D temp(1900,1,1);
return dist( temp, d )%7+1;
}

int print(int year, int mon ){//输出某月日历
D d(year, mon, 1 );
int week = xingqiji(d);
int sum = month[ mon ];
for( int i = 1; i < week; i++ )
cout << "    ";
for( int i = 1; i <= sum; i++){
cout << i << "    ";
if( week == 7 ){
week = 1;
cout << endl;
}
else week++;
}
cout << endl;
}

int main(void){
D a(2015,3,5);
cout << xingqiji(a) << endl;
print(2015,3);
return 0;
}