Can Someone help me with this PYTHON problem! please answer with code! Overview¶

Question

Can Someone help me with this PYTHON problem! please answer with code!

Overview¶

For this assignment you will implement a circular, array-backed queue data structure.

In the following class, which you are to complete, the backing array will be created and populated with Nones in the __init__ method, and the head and tail indexes set to sentinel values (you shouldn't need to modify __init__). Enqueueing and Dequeueing items will take place at the tail and head, with tail and head tracking the position of the most recently enqueued item and that of the next item to dequeue, respectively. To simplify testing, your implementation should make sure that when dequeuing an item its slot in the array is reset to None, and when the queue is emptied its head and tail attributes should be set to -1.

Because of the fixed size backing array, the enqueue operation is defined to raise a RuntimeError when the queue is full — the same exception should be raised when dequeue is called on an empty queue.

Finally, the resize method will allow the array underlying the queue to be increased in size. It is up to you how to implement this (you can either leave the elements in their current positions, though this may require "unwrapping" elements, or you can simply move all elements towards the front of the array). You may assume that resize will only be called with a value greater than the current length of the underlying array.

In [ ]:

. . .

In [ ]:

. . .

In [ ]:

. . .

In [ ]:

Explanation / Answer

Circular Array Backed Queue.py

class Queue:
    def __init__(self, limit=10):
        self.data = [None] * limit
        self.head = -1
        self.tail = -1

    def enqueue(self, val):

        if self.head - self.tail == 1:
            raise RuntimeError

        if len(self.data) - 1 == self.tail and self.head == 0:
            raise RuntimeError

        if self.head == -1 and self.tail == -1:
            self.data[0] = val
            self.head = 0
            self.tail = 0
        else:
            if len(self.data) - 1 == self.tail and self.head != 0:
                self.tail = -1
            self.data[self.tail + 1] = val
            self.tail = self.tail + 1

    def dequeue(self):

        if self.head == self.tail:
            temp = self.head
            self.head = -1
            self.tail = -1
            return self.data[temp]

        if self.head == -1 and self.tail == -1:
            raise RuntimeError
        if self.head != len(self.data):
            ret = self.data[self.head]
            self.data[self.head] = None
            self.head = self.head + 1
        else:
            # resetting head
            self.head = 0
            ret = self.data[self.head]
            self.data[self.head] = None
            self.head = self.head + 1
        return ret

    def resize(self, newsize):
        assert (len(self.data) < newsize)
        newdata = [None] * newsize
        head = self.head
        current = self.data[head]
        count = 0
        while current != None:
            newdata[count] = current
            count += 1
            if count != 0 and head == self.tail:
                break
            if head != len(self.data) - 1:
                head = head + 1
                current = self.data[head]
            else:
                head = 0
                current = self.data[head]
        self.data = newdata
        self.head = 0
        self.tail = count - 1

    def empty(self):
        if self.head == -1 and self.tail == -1:
            return True
        return False

    def __bool__(self):
        return not self.empty()

    def __str__(self):
        if not (self):
            return ''
        return ', '.join(str(x) for x in self)

    def __repr__(self):
        return str(self)

    def __iter__(self):
        head = self.head
        current = self.data[head]
        count = 0
        while current != None:
            yield current
            count += 1
            if count != 0 and head == self.tail:
                break
            if head != len(self.data) - 1:
                head = head + 1
                current = self.data[head]
            else:
                head = 0
                current = self.data[head]

Related Questions

Navigate

• Browse (All)
• Browse C
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.