Design Authentication Manager — LeetCode 1797 Python Solution

The problem

There is an authentication system that works with authentication tokens. For each session, the user will receive a new authentication token that will expire timeToLive seconds after the currentTime.

Example

Input

["AuthenticationManager", "renew", "generate", "countUnexpiredTokens", "generate", "renew", "renew", "countUnexpiredTokens"]

Output

[null, null, null, 1, null, null, null, 0]

Explanation

AuthenticationManager authenticationManager = new AuthenticationManager(5); // Constructs the AuthenticationManager with timeToLive = 5 seconds.

Python solution

class AuthenticationManager:
    def __init__(self, timeToLive: int):
        self.t = timeToLive
        self.d = defaultdict(int)

    def generate(self, tokenId: str, currentTime: int) -> None:
        self.d[tokenId] = currentTime + self.t

    def renew(self, tokenId: str, currentTime: int) -> None:
        if self.d[tokenId] <= currentTime:
            return
        self.d[tokenId] = currentTime + self.t

    def countUnexpiredTokens(self, currentTime: int) -> int:
        return sum(exp > currentTime for exp in self.d.values())


# Your AuthenticationManager object will be instantiated and called as such:
# obj = AuthenticationManager(timeToLive)
# obj.generate(tokenId,currentTime)
# obj.renew(tokenId,currentTime)
# param_3 = obj.countUnexpiredTokens(currentTime)

Complexity

Pattern: Linked List

Rewire pointers in place, with a dummy head and a saved next to keep it safe. LeetCode 1797. Design Authentication Manager is filed here because LeetCode tags it Linked List and Doubly-Linked List, which is the vocabulary this hub collects.

The linked list guide has the Python template for the pattern and the 75 LeetCode problems that use it.

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