Day of the Year — LeetCode 1154 Python Solution

The problem

Given a string date representing a Gregorian calendar date formatted as YYYY-MM-DD, return the day number of the year.

Example

Input

date = "2019-01-09"

Output

9

Explanation

Given date is the 9th day of the year in 2019.

Python solution

class Solution:
    def dayOfYear(self, date: str) -> int:
        y, m, d = (int(s) for s in date.split('-'))
        v = 29 if y % 400 == 0 or (y % 4 == 0 and y % 100) else 28
        days = [31, v, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]
        return sum(days[: m - 1]) + d

Complexity

Pattern: Math and Number Theory

Find the closed form, the invariant, or the modular identity — and skip the loop entirely. LeetCode 1154. Day of the Year is filed here on both counts: the reference solution below belongs to the algorithm family this hub collects, and LeetCode tags it Math.

The math and number theory guide has the Python template for the pattern and the 485 LeetCode problems that use it.

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