C语言实现万年历效果

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define str "  SUN  MON TUE  WED  THU  FRI  SAT  "
 
void menu();     //操作菜单
int leap(int year);    //判断某年是不是闰年
int days_month(int year, int month);    //返回某月的天数
int someday(int year, int month, int day);  //计算某天是星期几
void search_month(int year, int month);    //输出某月的日历
void search_someday(int year, int month, int day);  //查询某日是星期几
 
int main()
{
 int i, year, month, day;
 int k1, k2, k3, k4;  //用于判断输入的数据和操作是否正确，1代表正确，0代表错误
 int a = 1;
 menu();
 do
 {
 printf("请输入你要进行的操作(1-4):");
 scanf_s("%d", &i);
 getchar();
 switch (i)
 {
 case 1:
  printf("请输入你要查询的年份："); scanf_s("%d", &year);
  for (a; a <= 12; a++)
  {
  printf("nn---------*******  %d *******------------n", a);
  search_month(year, a);
  }
  printf("---------*********************------------nnn");
  break;
 
 
 case 2:
  printf("请输入您所要查询的相关信息.n");
  printf("年份："); scanf_s("%d", &year);
  printf("月份："); scanf_s("%d", &month);
  k1 = 1;
  while (k1)
  {
  if (month > 12 || month < 1)
  {
   printf("你输入的月份有误，请重新输入!n");
   printf("月份:");
   scanf_s("%d", &month);
   if (month < 1 || month>12)  k1 = 1;
  }
  else k1 = 0;
  }
  search_month(year, month);
  printf("---------*********************------------nnn");
  break;
 
 
 case 3:
  printf("请输入你要查询的日期n");
  printf("年份："); scanf_s("%d", &year);
  printf("月份："); scanf_s("%d", &month);
  k2 = 1;
  while (k2)
  {
  if (month > 12 || month < 1)
  {
   printf("你输入的月份有误，请重新输入!n");
   printf("月份:");
   scanf_s("%d", &month);
   if (month < 1 || month>12)  k2 = 1;
  }
  else k2 = 0;
  }
  //  printf("%d年%d月有%d天n",year,month,days_month(year,month));   调试观察输入的日期是否有误，可忽略
  printf("日期："); scanf_s("%d", &day);
  k3 = 1;
  while (k3)
  {
  if (day > days_month(year, month) || day < 1)
  {
   printf("你输入的日期有误，请重新输入!n");
   printf("日期:");
   scanf_s("%d", &day);
   if (day > days_month(year, month) || day < 1)  k3 = 1;
  }
  else k3 = 0;
  }
  search_someday(year, month, day);
  printf("---------*********************------------nnn"); break;
 
 
 case 4:exit(0);
  printf("---------*********************------------nnn"); break;
 
 
 default:
  k4 = 1;
  while (k4)
  {
  printf("你输入的数据有误，请重新输入你要进行的操作(1-4):");
  scanf_s("%d", &i);
  if (i < 1 || i>4)  k4 = 1;
  else k4 = 0;
  }
  break;
 }
 } while (i > 0 && i < 5);
 return 0;
}
 
void menu()
{
 int i = 1;
 printf("nntt----------------------------------------n");
 printf("tt|--------------------------------------|n");
 printf("tt|      %d. 输出某年的日历     |n", i);
 printf("tt|      %d. 输出某月的日历     |n", i + 1);
 printf("tt|      %d. 查询某日是星期几    |n", i + 2);
 printf("tt|      %d. 退出系统        |n", i + 3);
 printf("tt|--------------------------------------|n");
 printf("tt----------------------------------------nn");
 
}
 
int leap(int year)
{
 if ((year % 4 == 0 && year % 100 != 0) || year % 400 == 0) return 1;
 else return 0;
}
 
int days_month(int year, int month)
{
 int days_month;
 switch (month)
 {
 case 1:
 case 3:
 case 5:
 case 7:
 case 8:
 case 10:
 case 12: days_month = 31; break;
 
 case 4:
 case 6:
 case 9:
 case 11:days_month = 30; break;
 
 case 2:
 if (leap(year) == 1)
 {
  days_month = 29; break;
 }
 else days_month = 28; break;
 }
 return days_month;
}
 
int someday(int year, int month, int day)
{
 //该函数运用了特殊的计算公式，详细可参见 http://blog.163.com/hexin_mars_blog/blog/static/248215040201571351115699/
 int someday, m, n, i; //someday表示查询的日子是星期几
 m = year - year / 1000 * 1000;
 n = m - m / 100 * 100 - 1;      //用于获得年份的后两位数
 int days = 0;
 for (i = 1; i < month; i++) days = days + days_month(year, i);
 days = days + day;
 someday = (n + n / 4 - n / 100 + n / 400 + days) % 7;
 return someday;
}
 
void search_someday(int year, int month, int day)
{
 char weekname[20];
 switch (someday(year, month, day))
 {
 case 0:strcpy_s(weekname, "星期天"); break;
 case 1:strcpy_s(weekname, "星期一"); break;
 case 2:strcpy_s(weekname, "星期二"); break;
 case 3:strcpy_s(weekname, "星期三"); break;
 case 4:strcpy_s(weekname, "星期四"); break;
 case 5:strcpy_s(weekname, "星期五"); break;
 case 6:strcpy_s(weekname, "星期六"); break;
 }
 printf("你所要查询的日期是%sn", weekname);
}
 
void search_month(int year, int month)
{
 int i = 0, j, k = 0, m;   //j用于记录某月的第一天是星期几  m用于记录某月的天数 k用于换行提示
 char x[10] = "   ";
 m = days_month(year, month);
 j = someday(year, month, 1);
 
 //输出某月的日历
 printf("------------------------------------------n");
 printf("%sn", str);
 for (; i < j; i++)
 {
 printf("%s", x); k++;
 }
 for (i = 1; i <= m; i++)
 {
 k++;
 if (k % 7 == 0)
 {
  if (i < 10)
  {
  printf("  %d ", i);
  printf("n");
  }
  else if (i >= 10)
  {
  printf("  %d ", i);
  printf("n");
  }
 }
 else
 {
  if (i < 10)
  {
  printf("  %d ", i);
  }
  else if (i >= 10)
  {
  printf("  %d ", i);
  }
 }
 }
 printf("n------------------------------------------n");
}
 
void exit()
{
 exit(0);
}