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* Added documentations * Update data_structures/queue/circular_queue.py --------- Co-authored-by: Christian Clauss <cclauss@me.com>
98 lines
2.7 KiB
Python
98 lines
2.7 KiB
Python
# Implementation of Circular Queue (using Python lists)
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class CircularQueue:
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"""Circular FIFO queue with a fixed capacity"""
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def __init__(self, n: int):
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self.n = n
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self.array = [None] * self.n
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self.front = 0 # index of the first element
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self.rear = 0
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self.size = 0
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def __len__(self) -> int:
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"""
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>>> cq = CircularQueue(5)
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>>> len(cq)
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0
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>>> cq.enqueue("A") # doctest: +ELLIPSIS
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<data_structures.queue.circular_queue.CircularQueue object at ...
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>>> len(cq)
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1
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"""
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return self.size
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def is_empty(self) -> bool:
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"""
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Checks whether the queue is empty or not
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>>> cq = CircularQueue(5)
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>>> cq.is_empty()
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True
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>>> cq.enqueue("A").is_empty()
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False
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"""
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return self.size == 0
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def first(self):
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"""
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Returns the first element of the queue
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>>> cq = CircularQueue(5)
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>>> cq.first()
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False
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>>> cq.enqueue("A").first()
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'A'
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"""
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return False if self.is_empty() else self.array[self.front]
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def enqueue(self, data):
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"""
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This function inserts an element at the end of the queue using self.rear value
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as an index.
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>>> cq = CircularQueue(5)
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>>> cq.enqueue("A") # doctest: +ELLIPSIS
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<data_structures.queue.circular_queue.CircularQueue object at ...
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>>> (cq.size, cq.first())
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(1, 'A')
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>>> cq.enqueue("B") # doctest: +ELLIPSIS
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<data_structures.queue.circular_queue.CircularQueue object at ...
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>>> (cq.size, cq.first())
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(2, 'A')
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"""
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if self.size >= self.n:
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raise Exception("QUEUE IS FULL")
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self.array[self.rear] = data
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self.rear = (self.rear + 1) % self.n
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self.size += 1
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return self
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def dequeue(self):
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"""
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This function removes an element from the queue using on self.front value as an
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index and returns it
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>>> cq = CircularQueue(5)
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>>> cq.dequeue()
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Traceback (most recent call last):
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...
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Exception: UNDERFLOW
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>>> cq.enqueue("A").enqueue("B").dequeue()
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'A'
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>>> (cq.size, cq.first())
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(1, 'B')
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>>> cq.dequeue()
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'B'
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>>> cq.dequeue()
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Traceback (most recent call last):
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...
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Exception: UNDERFLOW
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"""
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if self.size == 0:
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raise Exception("UNDERFLOW")
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temp = self.array[self.front]
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self.array[self.front] = None
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self.front = (self.front + 1) % self.n
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self.size -= 1
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return temp
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