How hard is LeetCode 1115. Print FooBar Alternately?

LeetCode 1115. Print FooBar Alternately is rated Medium on LeetCode.

What is the time complexity of LeetCode 1115. Print FooBar Alternately?

The Python solution on this page runs in O(n).

What is the space complexity of LeetCode 1115. Print FooBar Alternately?

The Python solution on this page uses O(1) auxiliary space.

What topics does LeetCode 1115. Print FooBar Alternately cover?

LeetCode 1115. Print FooBar Alternately is tagged Concurrency on LeetCode.

Print FooBar Alternately — LeetCode 1115 Python Solution

MediumConcurrency

Problem: #1115
Reading time: 4 min
Source: leetcode.com

The problem

Suppose you are given the following code: class FooBar { public void foo() { for (int i = 0; i < n; i++) { print("foo"); } } public void bar() { for (int i = 0; i < n; i++) { print("bar"); } } } The same instance of FooBar will be passed to two different threads: thread A will call foo(), while thread B will call bar(). Modify the given program to output "foobar" n times.

Example

class FooBar {
  public void foo() {
    for (int i = 0; i < n; i++) {
      print("foo");
    }
  }

  public void bar() {
    for (int i = 0; i < n; i++) {
      print("bar");
    }
  }
}

Python solution

Python

from threading import Semaphore


class FooBar:
    def __init__(self, n):
        self.n = n
        self.f = Semaphore(1)
        self.b = Semaphore(0)

    def foo(self, printFoo: "Callable[[], None]") -> None:
        for _ in range(self.n):
            self.f.acquire()
            # printFoo() outputs "foo". Do not change or remove this line.
            printFoo()
            self.b.release()

    def bar(self, printBar: "Callable[[], None]") -> None:
        for _ in range(self.n):
            self.b.acquire()
            # printBar() outputs "bar". Do not change or remove this line.
            printBar()
            self.f.release()

Complexity

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

Frequently asked questions

How hard is LeetCode 1115. Print FooBar Alternately?: LeetCode 1115. Print FooBar Alternately is rated Medium on LeetCode.
What is the time complexity of LeetCode 1115. Print FooBar Alternately?: The Python solution on this page runs in O(n).
What is the space complexity of LeetCode 1115. Print FooBar Alternately?: The Python solution on this page uses O(1) auxiliary space.
What topics does LeetCode 1115. Print FooBar Alternately cover?: LeetCode 1115. Print FooBar Alternately is tagged Concurrency on LeetCode.