有以下程序 #include<iostream> using namespace std; static int days []={31,28,31,30,31,30,3l,31,30,31,30,31}; class date { private: int month,day,year; public: date(int m,int d,int y) { month=m; day=d; year=y; } date() {} void disp() { cout<<year<<'-'<<month<<'-'<<day<<end1; } date operator+(int day) { date dt=*this; day+=dt.day; while(day>days[dt.month-1]) { day-=days[dt.month-1]; if(++dt.month==13) { dt.month=1; dt.year++; } } dt.day=day; retrn dt; } }; int main() { date d1(6,20,2004),d2; d2=d1+20; d2.disp(); return 0; } 执行后的输出结果是