The Number of Full Rounds You Have Played — LeetCode 1904 Python Solution

The problem

You are participating in an online chess tournament. There is a chess round that starts every 15 minutes.

Example

Input

loginTime = "09:31", logoutTime = "10:14"

Output

1

Explanation

You played one full round from 09:45 to 10:00.

Python solution

class Solution:
    def numberOfRounds(self, loginTime: str, logoutTime: str) -> int:
        def f(s: str) -> int:
            return int(s[:2]) * 60 + int(s[3:])

        a, b = f(loginTime), f(logoutTime)
        if a > b:
            b += 1440
        a, b = (a + 14) // 15, b // 15
        return max(0, b - a)

Complexity

Pattern: Math and Number Theory

Find the closed form, the invariant, or the modular identity — and skip the loop entirely. LeetCode 1904. The Number of Full Rounds You Have Played 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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