我試圖制作一個程式來顯示特定年份的給定月份的日歷，但我真的找不到可以找到該月第一天的演算法。
我的程式：
#include <stdio.h>
#include <stdlib.h>
int get_first_weekDay(int year, int months1, int monthDays[months1])
{
int day;
int months2 = monthDays[months1];
int beginning = 3;
while(months1 > 0)
{
months2 = months2 monthDays[months1];
months1 = months1 - 1;
}
for (int i = 1800; i < year; i )
{
if ((i % 4 == 0 && year % 100 != 0) || year % 400 == 0)
{
beginning = beginning 366;
}
else
{
beginning = beginning 365;
}
}
day = (beginning months2) % 7;
return day;
}
int main(int argc, char* argv[])
{
if(argc != 3)
{
printf("Usage: ./calendar year month \n");
return 1;
}
int year = atoi(argv[1]);
int months1 = atoi(argv[2]) - 1;
int day = 0, dayInMonth, weekDay = 0, startingDay ,month;
char *months[] = {"Jan","Feb","Mar","Apr","May","Jun","Jul","Aug","Sep","Oct","Nov","Dec"};
int monthDays[] = {31,28,31,30,31,30,31,31,30,31,30,31};
if (argc == 3)
{
if((year % 4 == 0 && year % 100 != 0) || year % 400 == 0)
{
monthDays[1] = 29;
}
startingDay = get_first_weekDay(year, months1, &monthDays[months1]);
for(month = 0; month < 12; month )
{
if(months1 == month)
{
dayInMonth = monthDays[month] 1;
printf(" %s %d \n ---------------------------", months[month], year);
printf("\n Sun Mon Tue Wed Thu Fri Sat\n");
for(weekDay = 0; weekDay < startingDay; weekDay )
{
printf(" ");
}
for(day = 1; day < dayInMonth; day )
{
printf("M", day);
if( weekDay > 6)
{
printf("\n");
weekDay = 0;
}
startingDay = weekDay;
}
}
}
printf("\n");
return 1;
}
}
例如，如果我想知道 1800 年的第 1 個月，它會給我作為輸出：
~/calendar/ $ ./calendar 1800 1
Jan 1800
---------------------------
Sun Mon Tue Wed Thu Fri Sat
1
2 3 4 5 6 7 8
9 10 11 12 13 14 15
16 17 18 19 20 21 22
23 24 25 26 27 28 29
30 31
但不正確，因為 1800 年 1 月的第一天不是星期六。 日歷 1800
有人可以幫我找到這樣的演算法。我真的很感激！
uj5u.com熱心網友回復：
你在月份處理上有一個錯誤。您正在列印 1800 年 2 月。
int months2 = monthDays[months1];
應該
int months2 = 0;
在理解代碼的作用后，這很容易除錯。
代碼以 Wed ( int beginning = 3;)開頭。
然后，從 1800 年開始，將每年的天數添加到指定年份。
然后將每個月的天數添加到指定月份之前。
所以它應該在 1800 年 1 月加零。
這就是它試圖做的，至少。那么它為什么會回來6呢？好吧，很容易確認從未進入回圈。這是對的。而且很容易看到它在 1 月之前的幾個月中增加了非零天數。嗯，這顯然是錯誤的。
年的處理也有問題。
(i % 4 == 0 && year % 100 != 0) || year % 400 == 0
應該
(i % 4 == 0 && i % 100 != 0) || i % 400 == 0
清理完畢：
#include <stdio.h>
#include <stdlib.h>
static const char *months[] = {"Jan","Feb","Mar","Apr","May","Jun","Jul","Aug","Sep","Oct","Nov","Dec"};
static const int monthDays[] = {31,28,31,30,31,30,31,31,30,31,30,31};
// Returns 0 or 1
static int is_leap_year(int year) {
return (year % 4 == 0 && year % 100 != 0) || year % 400 == 0;
}
static int get_days_in_month(int year, int month0) {
if (month0 == 1) {
int leap_days = is_leap_year(year);
return 28 leap_days;
} else {
return monthDays[month0];
}
}
static int get_dow(int year, int month0, int day) {
int dow = 3; // 1800-01-01 is a Wednesday.
// For each year up to provided year (exclusive), starting with 1800.
while (year-- > 1800) {
int leap_days = is_leap_year(year);
dow = 365 leap_days;
}
// For each month up to provided month (exclusive)
while (month0--)
dow = monthDays[month0];
// For each day up to the provided day (exlcusive)
dow = day - 1;
return dow % 7;
}
int main(int argc, char* argv[]) {
if(argc != 3) {
fprintf(stderr, "Usage: ./calendar year month \n");
return 1;
}
int year = atoi(argv[1]);
int month0 = atoi(argv[2]) - 1; // 0-based month
int day = 1; // 1-based day
int dow = get_dow(year, month0, day);
int num_days = get_days_in_month(year, month0);
printf(" %s %d\n", months[month0], year);
printf(" ---------------------------\n");
printf(" Sun Mon Tue Wed Thu Fri Sat\n");
for (int i=0; i<dow; i)
printf(" ");
while (day <= num_days) {
printf("M", day );
dow = ( dow 1 ) % 7;
if (!dow)
printf("\n");
}
if (dow)
printf("\n");
return 0;
}
uj5u.com熱心網友回復：
for (int i = 1800; i < year; i )
{
...
if ((i % 4 == 0 && year % 100 != 0) || year % 400 == 0)
}
目前尚不清楚上述公式試圖計算什么。看起來像閏年計算，但year應該是i。
該函式get_first_weekDay需要一個陣列作為第三個引數。但你稱它為
startingDay = get_first_weekDay(year, months1, &monthDays[months1]);
修復這些錯誤似乎沒有多大作用。其余的計算相當混亂。我重寫了函式get_first_weekDay。請注意，它需要一個陣列輸入。
#include <stdio.h>
#include <stdlib.h>
int is_leap_year(int y)
{ return (y % 4 == 0 && y % 100 != 0) || (y % 400 == 0); }
int get_first_weekday(int year, int month, int days_in_month[12])
{
int beginning = 3; //1800, Jan, 1 is wedndsay (3)
for (int y = 1800; y < year; y )
beginning = is_leap_year(y) ? 366 : 365;
for (int m = 0; m < month; m )
beginning = days_in_month[m];
return beginning % 7;
}
void print_calendar(int year, int month)
{
month--;
const char* months[] = { "Jan","Feb","Mar","Apr","May","Jun",
"Jul","Aug","Sep","Oct","Nov","Dec" };
int days_in_month[] = { 31,28,31,30,31,30,31,31,30,31,30,31 };
if (is_leap_year(year))
days_in_month[1] = 29;
int first_week_day = get_first_weekday(year, month, days_in_month);
printf(" %s %d \n", months[month], year);
printf(" ---------------------------\n");
printf(" Sun Mon Tue Wed Thu Fri Sat\n");
for (int wkday = 0; wkday < first_week_day; wkday )
printf(" ");
for (int day = 1; day < days_in_month[month] 1; day )
{
printf("M", day);
if(((day first_week_day) % 7) == 0)
printf("\n");
}
printf("\n\n");
}
int main(void)
{
for (int m = 1; m < 4; m ) print_calendar(1800, m);
for (int m = 8; m <= 12; m ) print_calendar(2021, m);
return 0;
}
跑
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