# 1116. Print Zero Even Odd

### 題目敘述

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`

### 解法解析

#### 程式範例

##### Python
``````from threading import Lock

class ZeroEvenOdd:
def __init__(self, n):
self.n = n

self.zero_mutex = Lock()
self.odd_mutex = Lock()
self.even_mutex = Lock()

self.even_mutex.acquire()
self.odd_mutex.acquire()

# printNumber(x) outputs "x", where x is an integer.
def zero(self, printNumber: 'Callable[[int], None]') -> None:
for i in range(self.n):
self.zero_mutex.acquire()

printNumber(0)

if (i % 2) == 0:
self.even_mutex.release()
else:
self.odd_mutex.release()

def even(self, printNumber: 'Callable[[int], None]') -> None:
for i in range(2, self.n + 1, 2):
self.odd_mutex.acquire()
printNumber(i)
self.zero_mutex.release()
self.odd_mutex.release()

def odd(self, printNumber: 'Callable[[int], None]') -> None:
for i in range(1, self.n + 1, 2):
self.even_mutex.acquire()
printNumber(i)
self.zero_mutex.release()
self.even_mutex.release()
``````