init commit

3sem/cnts/contest7/05.c

@@ -0,0 +1,104 @@
+#include <stdio.h>
+#include <time.h>
+
+enum
+{
+    SYNODIC_PERIOD_DAYS = 29,
+    SYNODIC_PERIOD_HOURS = 12,
+    SYNODIC_PERIOD_MINUTES = 44,
+    FULL_MOON_YEAR = 2021,
+    FULL_MOON_MONTH = 5,
+    FULL_MOON_DAY = 26,
+    FULL_MOON_HOUR = 11,
+    FULL_MOON_MINUTE = 14,
+};
+
+void
+add_synodic_period(struct tm *tm)
+{
+    tm->tm_mday += SYNODIC_PERIOD_DAYS;
+    tm->tm_hour += SYNODIC_PERIOD_HOURS;
+    tm->tm_min += SYNODIC_PERIOD_MINUTES;
+    timegm(tm);
+}
+
+void
+sub_synodic_period(struct tm *tm)
+{
+    tm->tm_mday -= SYNODIC_PERIOD_DAYS;
+    tm->tm_hour -= SYNODIC_PERIOD_HOURS;
+    tm->tm_min -= SYNODIC_PERIOD_MINUTES;
+    timegm(tm);
+}
+
+struct tm
+find_full_moon_after(struct tm start)
+{
+    struct tm full_moon = {0};
+    full_moon.tm_isdst = -1;
+    full_moon.tm_year = FULL_MOON_YEAR - 1900;
+    full_moon.tm_mon = FULL_MOON_MONTH - 1;
+    full_moon.tm_mday = FULL_MOON_DAY;
+    full_moon.tm_hour = FULL_MOON_HOUR;
+    full_moon.tm_min = FULL_MOON_MINUTE;
+    timegm(&full_moon);
+
+    while (timegm(&full_moon) < timegm(&start)) {
+        add_synodic_period(&full_moon);
+    }
+
+    while (timegm(&full_moon) > timegm(&start)) {
+        sub_synodic_period(&full_moon);
+    }
+
+    add_synodic_period(&full_moon);
+
+    return full_moon;
+}
+
+struct tm
+find_fourth_monday_after(struct tm start)
+{
+    struct tm date = start;
+    date.tm_mday++;
+
+    int num_of_mondays = 0;
+    while (num_of_mondays < 4) {
+        timegm(&date);
+
+        if (date.tm_wday == 1) {
+            num_of_mondays++;
+        }
+
+        date.tm_mday++;
+    }
+
+    date.tm_mday--;
+
+    timegm(&date);
+
+    return date;
+}
+
+int
+main()
+{
+    int year;
+    if (scanf("%d", &year) != 1) {
+        return 1;
+    }
+
+    struct tm start = {0};
+    start.tm_isdst = -1;
+    start.tm_year = year - 1900;
+    start.tm_mday = 257;
+
+    timegm(&start);
+
+    struct tm full_moon = find_full_moon_after(start);
+    struct tm event_date = find_fourth_monday_after(full_moon);
+
+    printf("%04d-%02d-%02d\n", event_date.tm_year + 1900, event_date.tm_mon + 1, event_date.tm_mday);
+
+    return 0;
+}