1360. Number of Days Between Two Dates

Problem

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.

Solution (Java)

class Solution {
    public int daysBetweenDates(String date1, String date2) {
        String[] strings1 = date1.split("-");
        String[] strings2 = date2.split("-");
        return Math.abs(
                julianDay(
                                Integer.parseInt(strings1[0]),
                                Integer.parseInt(strings1[1]),
                                Integer.parseInt(strings1[2]))
                        - julianDay(
                                Integer.parseInt(strings2[0]),
                                Integer.parseInt(strings2[1]),
                                Integer.parseInt(strings2[2])));
    }

    private int julianDay(int year, int month, int day) {
        int a = (14 - month) / 12;
        int y = year + 4800 - a;
        int m = month + 12 * a - 3;
        return day + (153 * m + 2) / 5 + 365 * y + y / 4 - y / 100 + y / 400 - 32045;
    }
}

Explain:

nope.

Complexity:

• Time complexity : O(n).
• Space complexity : O(n).