问题：
方法： 最简单的解法是蔡勒公式，具体推导过程可以搜索。下面是暴力解法，通过选取1970年12月31日作为原点，然后计算间隔的日数，对7进行除余可得具体的星期数。
class DayOfTheWeek {
fun dayOfTheWeek(day: Int, month: Int, year: Int): String {
var cal = 0
val months = arrayOf(31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31)
for (index in 1971 until year) {
if ((index % 4 == 0 && index % 100 != 0) || index % 400 == 0) {
cal += 366
} else {
cal += 365
}
}
if ((year % 4 == 0 && year % 100 != 0) || year % 400 == 0) {
months[1] = 29
}
for (index in 0 until month - 1) {
cal += months[index]
}
cal += day
when ((cal - 1) % 7) {
0 -> return "Friday"
1 -> return "Saturday"
2 -> return "Sunday"
3 -> return "Monday"
4 -> return "Tuesday"
5 -> return "Wednesday"
6 -> return "Thursday"
else -> return ""
}
}
}
fun main(args: Array<String>) {
val dayOfTheWeek = DayOfTheWeek()
print(dayOfTheWeek.dayOfTheWeek(31, 8, 2019))
}
有问题随时沟通
