Question

我一直试图使我的循环队列工作一段时间，只是想我问一个问题，看看我是否能得到任何提示。我的循环队列的问题是即使队列未满，insert方法也始终返回值False。这是我到目前为止所拥有的。

class CircularQueue:

    def __init__(self, size):
        """
        -------------------------------------------------------
        Initializes an empty queue. Data is stored in a list.
        -------------------------------------------------------
        Postconditions:
          Initializes an empty queue.
        -------------------------------------------------------
        """
        assert size>=0, "size must be >=0"
        self._values = [None] * size
        self._front = 0
        self._rear = 0
        self._size = size
        self.size = 0

        return 

    def __len__(self):
        """
        -------------------------------------------------------
        Returns the size of the queue.
        Use: n = len( q )
        -------------------------------------------------------
        Postconditions:
          Returns the number of values in the queue.
        -------------------------------------------------------
        """
        return len(self._values())


  def is_full(self):
          value = self._rear - self._size
          if self._values[value]==None:
                 full = False
    else:
        full = True
    return full
    def is_empty(self):
        """
        -------------------------------------------------------
        Determines if the queue is empty.
        Use: b = q.is_empty()
        -------------------------------------------------------
        Postconditions:
          Returns True if the queue is empty, False otherwise.
        -------------------------------------------------------
        """
        if len(self._values) == 0:
            empty = True
        else:
            empty = False
        return empty

    def insert(self, value):
        """
        -------------------------------------------------------
        Inserts a copy of value into the queue.
        Use: q.insert( value )
        -------------------------------------------------------
        Preconditions:
          value - a data element (?)
        Postconditions:
          value is added to the rear of the queue.
        -------------------------------------------------------
        """
        if self.is_full() == True:
            inserted = False
        else:
            inserted = True
            self._values[self._rear] = value
            self._rear = (self._rear + 1)% self._size

        return inserted

    def remove( self ):
        """
        -------------------------------------------------------
        Removes and returns value from the queue.
        Use: v = q.remove()
        -------------------------------------------------------
        Postconditions:
          Returns the value at the front of queue - the value is
          removed from queue. Returns None if queue is empty.
        -------------------------------------------------------
        """
        if self.is_empty() == False:
            value = copy.deepcopy(self._values[self._front])
            self._front = (self._front + 1) % self._size
        else:
            value = None

        return value

    def peek(self):
        """
        -------------------------------------------------------
        Peeks at the front of queue.
        Use: v = q.peek()
        -------------------------------------------------------
        Postconditions:
          Returns a copy of the value at the front of queue -
          the value is not removed from queue. Returns None
          if queue is empty.
        -------------------------------------------------------
        """

        if self.is_empty() == True:
            value = None
        else:
            value = copy.deepcopy(self._values[self._front])

        return value

    def print_i(self):
        """
        -------------------------------------------------------
        Prints the contents of queue from front to rear.
        Use: q.print_i()
        -------------------------------------------------------
        Postconditions:
          Prints each value in queue from front to rear.
          Each value starts on a new line.
        -------------------------------------------------------
        """
        for i in range(len(self._values)):
            print(self._values[i])
        return

我刚开始尝试测试它，所以这就是我的测试模块。

from circularqueue import CircularQueue

q = CircularQueue(10)

value = q.insert(1)

print(value)

我试图在这里做的就是查看我的insert方法是否会返回True，因为我知道队列未满，因为这是我尝试输入的第一个值。任何提示？

Answer 1

您将_front和_rear初始化为0，因此您的is_full检查从一开始就返回True。

循环队列Python实现

1 个答案: