[LC] 1360. Number of Days Between Two Dates

Write a program to count the number of days between two dates.

The two dates are given as strings, their format is YYYY-MM-DD as shown in the examples.

Example 1:

Input: date1 = "2019-06-29", date2 = "2019-06-30"
Output: 1

Example 2:

Input: date1 = "2020-01-15", date2 = "2019-12-31"
Output: 15

Constraints:

• The given dates are valid dates between the years 1971 and 2100.

class Solution {
    public int daysBetweenDates(String date1, String date2) {
        return Math.abs(calculateDays(date1) - calculateDays(date2));
    }
    
    private int calculateDays(String date) {
        int[] monthDays = {0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
        String[] dateArr = date.split("-");
        int year = Integer.parseInt(dateArr[0]);
        int month = Integer.parseInt(dateArr[1]);
        int day = Integer.parseInt(dateArr[2]);
        int res = day;
        for (int i = 1971; i < year; i++) {
            if (isLeap(i)) {
                res += 366;
            } else {
                res += 365;
            }
        }
        for (int i = 1; i < month; i++) {
            if (isLeap(year) && i == 2) {
                res += 1;
            }
            res += monthDays[i];
        }
        return res;
    }
    
    private boolean isLeap(int year) {
        return (year % 4 == 0 && year % 100 != 0) || year % 400 == 0;
    }
}