add: 220103-CN

2201/220103-CN.cpp

@@ -0,0 +1,52 @@
+#include <iostream>
+#include <string>
+
+/**
+ * #1185. Day of the Week
+ * Given a date, return the corresponding day of the week for that date.
+ * The input is given as three integers representing the day, month and year respectively.
+ * Return the answer as one of the following values {"Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"}.
+ *
+ * Input: day = 18, month = 7, year = 1999
+ * Output: "Sunday"
+ *
+ * Range: year <- [1971, 2100]
+ */
+
+class Solution {
+private:
+	inline static const std::string weekName[7] = {
+			"Sunday",
+			"Monday",
+			"Tuesday",
+			"Wednesday",
+			"Thursday",
+			"Friday",
+			"Saturday"
+	};
+	inline static const int monthDays[12] = {0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334};
+public:
+	static std::string dayOfTheWeek(int day, int month, int year) {
+		// Starts at 1969-01-01 [Wednesday]
+		// (365 * 4 + 1) % 7 == 5, 365 % 7 == 1
+		// 1969, +1 ~ +3 will not experience leap years.
+		return weekName[(3 + (((year - 1969) >> 2) * 5) + ((year - 1969) & 3) + monthDays[month - 1] + day - 1 + (((year - 1969) & 3) == 3 && month > 2 && year != 2100 ? 1 : 0)) % 7];
+	}
+};
+
+int main() {
+	int n[12] {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
+	int ans, prev = 4;
+	for (int y = 1971; y <= 2100; ++y) {
+		for (int m = 1; m <= 12; ++m) {
+			for (int d = 1; d <= ((!(y & 3) && m == 2 && y != 2100) ? 29 : n[m - 1]); ++d) {
+				if ((ans = /* Solution::dayOfTheWeek(d, m, y) int when debug */ 0) != (prev = (prev + 1) % 7)) {
+					std::printf("%d-%02d-%02d -> %d != %d\n", y, m, d, ans, prev);
+					std::printf("ILLEGAL!\n");
+					return 1;
+				}
+			}
+		}
+	}
+	return 0;
+}

2201/CMakeLists.txt

@@ -3,4 +3,4 @@ PROJECT(2201)
 
 SET(CMAKE_CXX_STANDARD 23)
 
-ADD_EXECUTABLE(2201 220102.cpp)
+ADD_EXECUTABLE(2201 220103-CN.cpp)