Algorithm

Problem Name: 1116. Print Zero Even Odd

Problem Link: https://leetcode.com/problems/print-zero-even-odd/
 

You have a function printNumber that can be called with an integer parameter and prints it to the console.

  • For example, calling printNumber(7) prints 7 to the console.

You are given an instance of the class ZeroEvenOdd that has three functions: zero, even, and odd. The same instance of ZeroEvenOdd will be passed to three different threads:

  • Thread A: calls zero() that should only output 0's.
  • Thread B: calls even() that should only output even numbers.
  • Thread C: calls odd() that should only output odd numbers.

Modify the given class to output the series "010203040506..." where the length of the series must be 2n.

Implement the ZeroEvenOdd class:

  • ZeroEvenOdd(int n) Initializes the object with the number n that represents the numbers that should be printed.
  • void zero(printNumber) Calls printNumber to output one zero.
  • void even(printNumber) Calls printNumber to output one even number.
  • void odd(printNumber) Calls printNumber to output one odd number.

 

Example 1:

Input: n = 2
Output: "0102"
Explanation: There are three threads being fired asynchronously.
One of them calls zero(), the other calls even(), and the last one calls odd().
"0102" is the correct output.

Example 2:

Input: n = 5
Output: "0102030405"

 

Constraints:

  • 1 <= n <= 1000

Code Examples

#1 Code Example with Python Programming

Code - Python Programming


import threading


class ZeroEvenOdd:
    def __init__(self, n):
        self.n = n
        self.z = threading.Semaphore()
        self.e = threading.Semaphore()
        self.o = threading.Semaphore()
        self.e.acquire()
        self.o.acquire()
        self.cur = 1
        
	# printNumber(x) outputs "x", where x is an integer.
    def zero(self, printNumber: 'Callable[[int], None]') -> None:
        for _ in range(self.n):
            self.z.acquire()
            printNumber(0)
            if self.cur % 2:
                self.o.release()
            else:
                self.e.release()
        
        
    def even(self, printNumber: 'Callable[[int], None]') -> None:
        for _ in range(self.n // 2):
            self.e.acquire()
            printNumber(self.cur)
            self.cur += 1
            self.z.release()
        
    def odd(self, printNumber: 'Callable[[int], None]') -> None:
        for _ in range(self.n // 2 + self.n % 2):
            self.o.acquire()
            printNumber(self.cur)
            self.cur += 1
            self.z.release()
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Input

x
–
+
cmd
n = 2

Output

x
–
+
cmd
"0102"
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Demonstration

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