Leetcode #1904: The Number of Full Rounds You Have Played
In this guide, we solve Leetcode #1904 The Number of Full Rounds You Have Played in Python and focus on the core idea that makes the solution efficient.
You will see the intuition, the step-by-step method, and a clean Python implementation you can use in interviews.
Problem Statement
You are participating in an online chess tournament. There is a chess round that starts every 15 minutes.
Quick Facts
- Difficulty: Medium
- Premium: No
- Tags: Math, String
Intuition
There is a mathematical invariant or formula that directly leads to the result.
Using math avoids unnecessary loops and reduces complexity.
Approach
Derive the formula or update rule, then compute the answer directly.
Handle edge cases like overflow or zero carefully.
Steps:
- Identify the math relationship.
- Compute the result with a loop or formula.
- Handle edge cases.
Example
Input: loginTime = "09:31", logoutTime = "10:14"
Output: 1
Explanation: You played one full round from 09:45 to 10:00.
You did not play the full round from 09:30 to 09:45 because you logged in at 09:31 after it began.
You did not play the full round from 10:00 to 10:15 because you logged out at 10:14 before it ended.
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
The time complexity is , and the space complexity is . The space complexity is .
Edge Cases and Pitfalls
Watch for boundary values, empty inputs, and duplicate values where applicable. If the problem involves ordering or constraints, confirm the invariant is preserved at every step.
Summary
This Python solution focuses on the essential structure of the problem and keeps the implementation interview-friendly while meeting the constraints.