How hard is LeetCode 1117. Building H2O?

LeetCode 1117. Building H2O is rated Medium on LeetCode.

What topics does LeetCode 1117. Building H2O cover?

LeetCode 1117. Building H2O is tagged Concurrency on LeetCode.

Building H2O — LeetCode 1117 Python Solution

MediumConcurrency

Problem: #1117
Reading time: 3 min
Source: leetcode.com

The problem

There are two kinds of threads: oxygen and hydrogen. Your goal is to group these threads to form water molecules.

Example

Input: water = "HOH"
Output: "HHO"
Explanation: "HOH" and "OHH" are also valid answers.

Python solution

Python

from threading import Semaphore


class H2O:
    def __init__(self):
        self.h = Semaphore(2)
        self.o = Semaphore(0)

    def hydrogen(self, releaseHydrogen: "Callable[[], None]") -> None:
        self.h.acquire()
        # releaseHydrogen() outputs "H". Do not change or remove this line.
        releaseHydrogen()
        if self.h._value == 0:
            self.o.release()

    def oxygen(self, releaseOxygen: "Callable[[], None]") -> None:
        self.o.acquire()
        # releaseOxygen() outputs "O". Do not change or remove this line.
        releaseOxygen()
        self.h.release(2)

Complexity

Measure	Complexity
Time	O(n)
Space	O(1) to O(n) auxiliary

Frequently asked questions

How hard is LeetCode 1117. Building H2O?: LeetCode 1117. Building H2O is rated Medium on LeetCode.
What topics does LeetCode 1117. Building H2O cover?: LeetCode 1117. Building H2O is tagged Concurrency on LeetCode.