1118. Number of Days in a Month 🔒

Description

Given a year year and a month month, return the number of days of that month.

 

Example 1:

Input: year = 1992, month = 7
Output: 31

Example 2:

Input: year = 2000, month = 2
Output: 29

Example 3:

Input: year = 1900, month = 2
Output: 28

 

Constraints:

• 1583 <= year <= 2100
• 1 <= month <= 12

Solutions

Solution 1: Determine Leap Year

We can first determine whether the given year is a leap year. If the year can be divided by \(4\) but not by \(100\), or can be divided by \(400\), then this year is a leap year.

February has \(29\) days in a leap year and \(28\) days in a common year.

We can use an array \(days\) to store the number of days in each month of the current year, where \(days[0]=0\), \(days[i]\) represents the number of days in the \(i\)th month of the current year. Then the answer is \(days[month]\).

The time complexity is \(O(1)\), and the space complexity is \(O(1)\).

Python3JavaC++GoTypeScript

class Solution:
    def numberOfDays(self, year: int, month: int) -> int:
        leap = (year % 4 == 0 and year % 100 != 0) or (year % 400 == 0)
        days = [0, 31, 29 if leap else 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]
        return days[month]

class Solution {
    public int numberOfDays(int year, int month) {
        boolean leap = (year % 4 == 0 && year % 100 != 0) || (year % 400 == 0);
        int[] days = new int[] {0, 31, leap ? 29 : 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
        return days[month];
    }
}

class Solution {
public:
    int numberOfDays(int year, int month) {
        bool leap = (year % 4 == 0 && year % 100 != 0) || (year % 400 == 0);
        vector<int> days = {0, 31, leap ? 29 : 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
        return days[month];
    }
};

func numberOfDays(year int, month int) int {
    leap := (year%4 == 0 && year%100 != 0) || (year%400 == 0)
    x := 28
    if leap {
        x = 29
    }
    days := []int{0, 31, x, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}
    return days[month]
}

function numberOfDays(year: number, month: number): number {
    const leap = (year % 4 === 0 && year % 100 !== 0) || year % 400 === 0;
    const days = [0, 31, leap ? 29 : 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31];
    return days[month];
}

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