How to Compute the Number of Days in a Month?

Given a year Y and a month M, return how many days there are in that month.

Example 1:
Input: Y = 1992, M = 7
Output: 31

Example 2:
Input: Y = 2000, M = 2
Output: 29

Example 3:
Input: Y = 1900, M = 2
Output: 28

Note:
1583 <= Y <= 2100
1 <= M <= 12

The special case is the February: 29 days if it is a leap year and 28 days otherwise. All other months either have 30 or 31 days. Therefore, using a simple switch-statement in C/C++/Java should do it.

class Solution {
public:
    int numberOfDays(int Y, int M) {
        if (M == 2) {
            if (isLeap(Y)) return 29;
            return 28;
        }
        switch (M) {
            case 1:
            case 3:
            case 5:
            case 7:
            case 8:
            case 10:
            case 12:
                return 31;
        }
        return 30;
    }
private:
    bool isLeap(int Y) {
        if (Y % 400 == 0) {
            return true;
        } else if ( Y % 100 == 0) {
            return false;
        } else if (Y % 4 == 0) {
            return true;
        } else {
            return false;
        }        
    }
};

The above C++ program uses the isLeap method to test for leap year. And both the time and space complexity is O(1) constant.

–EOF (The Ultimate Computing & Technology Blog) —