LeetCode: Number of Days in a Month

// https://code.dennyzhang.com/number-of-days-in-a-month
// Basic Ideas: array
//  https://www.timeanddate.com/calendar/months/
// Complexity: Time O(1), Space O(1)
func numberOfDays(Y int, M int) int {
    l := []int{31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}
    if M == 2 {
        if (Y%4 ==0 && Y%100!=0) || (Y%400 == 0) {
            l[1] = 29
        }
    }
    return l[M-1]
}