日期计算

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 1 //日期处理
 2 
 3 //每个月的天数
 4 int days[12]={31,28,31,30,31,30,31,31,30,31,30,31};
 5 
 6 char* week[7]={"Sunday","Monday","Tuesday","Wednesday","Thursday","Friday","Saturday"};
 7 
 8 typedef struct Date
 9 {
10     int year;
11     int month;
12     int day;
13 }Date;
14 
15 //判断是否为闰年
16 //能被4整除却不能被100整除，或者能被400整除
17 bool isLeap(int year)
18 {
19     return ((year%4==0&&year%100)||(year%400==0));
20 }
21 
22 
23 //判断日期是否合法
24 bool isLegal(Date d)
25 {
26     if(d.month<0||d.month>12)
27         return false;
28     if(d.month==2)
29     {
30         if(isLeap(d.year))
31             return (d.day>0 && d.day<=29);
32         else
33             return (d.day>0 && d.day<=28);
34     }
35     else
36     {
37         return (d.day>0 && d.day<=days[d.mouth-1]);
38     }
39 }
40 
41 
42 
43 
44 //返回特定日期是星期几
45 int weekday(Date d)
46 {
47     int days=0;
48     for(int i=0;i<d.month-1;++i)
49     {
50         days+=days[i];        
51     }
52     if(d.month>2&&isLeap(d.year))
53         days++;
54     days+=d.day;
55     return ((d.year-1)+(int)((d.year-1)/4)-(int)((d.year-1)/100)+(int)((d.year-1)/400)+days)%7;
56 }