Data commit

Task/Doomsday-rule/Rust/doomsday-rule.rust

@@ -0,0 +1,43 @@
+fn day_of_week(year: u32, month: u32, day: u32) -> u32 {
+    const LEAPYEAR_FIRSTDOOMSDAYS: [u32; 12] = [4, 1, 7, 4, 2, 6, 4, 1, 5, 3, 7, 5];
+    const NONLEAPYEAR_FIRSTDOOMSDAYS: [u32; 12] = [3, 7, 7, 4, 2, 6, 4, 1, 5, 3, 7, 5];
+    assert!(year > 1581 && year < 10000);
+    assert!(month >= 1 && month <= 12);
+    assert!(day >= 1 && day <= 31);
+    let doomsday = (2 + 5 * (year % 4) + 4 * (year % 100) + 6 * (year % 400)) % 7;
+    let anchorday = if year % 4 != 0 || (year % 100 == 0 && year % 400 != 0) {
+        NONLEAPYEAR_FIRSTDOOMSDAYS[month as usize - 1]
+    } else {
+        LEAPYEAR_FIRSTDOOMSDAYS[month as usize - 1]
+    };
+    (doomsday + day + 7 - anchorday) % 7
+}
+
+fn print_day_of_week(year: u32, month: u32, day: u32) {
+    const DAY_NAMES: [&str; 7] = [
+        "Sunday",
+        "Monday",
+        "Tuesday",
+        "Wednesday",
+        "Thursday",
+        "Friday",
+        "Saturday",
+    ];
+    println!(
+        "{:04}-{:02}-{:02}: {}",
+        year,
+        month,
+        day,
+        DAY_NAMES[day_of_week(year, month, day) as usize]
+    );
+}
+
+fn main() {
+    print_day_of_week(1800, 1, 6);
+    print_day_of_week(1875, 3, 29);
+    print_day_of_week(1915, 12, 7);
+    print_day_of_week(1970, 12, 23);
+    print_day_of_week(2043, 5, 14);
+    print_day_of_week(2077, 2, 12);
+    print_day_of_week(2101, 4, 2);
+}