1195. Fizz Buzz Multithreaded

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1195. Fizz Buzz Multithreaded

Description

You have the four functions:

  • printFizz that prints the word "fizz" to the console,
  • printBuzz that prints the word "buzz" to the console,
  • printFizzBuzz that prints the word "fizzbuzz" to the console, and
  • printNumber that prints a given integer to the console.

You are given an instance of the class FizzBuzz that has four functions: fizz, buzz, fizzbuzz and number. The same instance of FizzBuzz will be passed to four different threads:

  • Thread A: calls fizz() that should output the word "fizz".
  • Thread B: calls buzz() that should output the word "buzz".
  • Thread C: calls fizzbuzz() that should output the word "fizzbuzz".
  • Thread D: calls number() that should only output the integers.

Modify the given class to output the series [1, 2, "fizz", 4, "buzz", ...] where the i^th token (1-indexed ) of the series is:

  • "fizzbuzz" if i is divisible by 3 and 5,
  • "fizz" if i is divisible by 3 and not 5,
  • "buzz" if i is divisible by 5 and not 3, or
  • i if i is not divisible by 3 or 5.

Implement the FizzBuzz class:

  • FizzBuzz(int n) Initializes the object with the number n that represents the length of the sequence that should be printed.
  • void fizz(printFizz) Calls printFizz to output "fizz".
  • void buzz(printBuzz) Calls printBuzz to output "buzz".
  • void fizzbuzz(printFizzBuzz) Calls printFizzBuzz to output "fizzbuzz".
  • void number(printNumber) Calls printnumber to output the numbers.

Example 1:

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Input: n = 15
Output: [1,2,"fizz",4,"buzz","fizz",7,8,"fizz","buzz",11,"fizz",13,14,"fizzbuzz"]

Example 2:

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Input: n = 5
Output: [1,2,"fizz",4,"buzz"]

Constraints:

  • 1 <= n <= 50

Hints/Notes

  • 2025/03/25 Q2
  • concurrency
  • No solution from 0x3F or Leetcode

Solution

Language: C++

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class FizzBuzz {
private:
    mutex m;
    condition_variable cv;
    int curIdx;
    int n;

public:
    FizzBuzz(int n) {
        this->n = n;
        this->curIdx = 1;
    }

    // printFizz() outputs "fizz".
    void fizz(function<void()> printFizz) {
        while (true) {
            unique_lock<mutex> lock(m);
            cv.wait(lock, [&]{
                return (curIdx % 3 == 0 && curIdx % 5 != 0) || curIdx > n;
            });
            if (curIdx > n) {
                return;
            }
            printFizz();
            curIdx++;
            cv.notify_all();
        }
    }

    // printBuzz() outputs "buzz".
    void buzz(function<void()> printBuzz) {
        while (true) {
            unique_lock<mutex> lock(m);
            cv.wait(lock, [&]{
                return (curIdx % 3 != 0 && curIdx % 5 == 0) || curIdx > n;
            });
            if (curIdx > n) {
                return;
            }
            printBuzz();
            curIdx++;
            cv.notify_all();
        }
    }

    // printFizzBuzz() outputs "fizzbuzz".
    void fizzbuzz(function<void()> printFizzBuzz) {
         while (true) {
            unique_lock<mutex> lock(m);
            cv.wait(lock, [&]{
                return (curIdx % 3 == 0 && curIdx % 5 == 0) || curIdx > n;
            });
            if (curIdx > n) {
                return;
            }
            printFizzBuzz();
            curIdx++;
            cv.notify_all();
        }
    }

    // printNumber(x) outputs "x", where x is an integer.
    void number(function<void(int)> printNumber) {
         while (true) {
            unique_lock<mutex> lock(m);
            cv.wait(lock, [&]{
                return (curIdx % 3 && curIdx % 5) || curIdx > n;
            });
            if (curIdx > n) {
                return;
            }
            printNumber(curIdx);
            curIdx++;
            cv.notify_all();
        }
    }
};