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This approach employs semaphores to control the execution order of methods. Since semaphores are synchronization constructs that can be used to control access to a common resource in a concurrent system, we can use them to gate the execution of 'second' and 'third' methods until 'first' and 'second' have completed, respectively. The semaphore for 'second' starts at 0 and is incremented by 'first', allowing 'second' to run. Similarly, 'third' can proceed only after 'second' increments its semaphore.
Time Complexity: O(1) for each method call. Space Complexity: O(1).
1using System;
2using System.Threading;
3
4public class Foo {
5 private SemaphoreSlim secondSemaphore = new SemaphoreSlim(0, 1);
6 private SemaphoreSlim thirdSemaphore = new SemaphoreSlim(0, 1);
7
8 public void First(Action printFirst) {
9 printFirst();
10 secondSemaphore.Release();
11 }
12
13 public void Second(Action printSecond) {
14 secondSemaphore.Wait();
15 printSecond();
16 thirdSemaphore.Release();
17 }
18
19 public void Third(Action printThird) {
20 thirdSemaphore.Wait();
21 printThird();
22 }
23}In C#, the SemaphoreSlim class is utilized. It functions similarly to Java and Python implementations, using waits and releases to properly synchronize the methods, ensuring 'second' can only proceed once 'first' has finished, and likewise 'third' requires 'second' to complete.
This approach leverages locks and condition variables to achieve the desired execution order. By associating each method with a condition variable, the appropriate method waits (and releases lock) until the previous condition is signaled, facilitating the required sequence.
Time Complexity: O(1) for each method call. Space Complexity: O(1).
1from threading import Lock, Condition
2
3class Foo
In Python, we use a lock with condition variables to ensure proper sequencing. The first method sets a flag and notifies other methods once it completes. Second waits until the first_done is True and proceeds similarly for third, which waits for second_done.