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130 lines
4.1 KiB
130 lines
4.1 KiB
"""
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File: array_deque.py
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Created Time: 2023-03-01
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Author: krahets (krahets@163.com)
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"""
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class ArrayDeque:
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"""Double-ended queue class based on circular array"""
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def __init__(self, capacity: int):
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"""Constructor"""
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self._nums: list[int] = [0] * capacity
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self._front: int = 0
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self._size: int = 0
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def capacity(self) -> int:
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"""Get the capacity of the double-ended queue"""
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return len(self._nums)
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def size(self) -> int:
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"""Get the length of the double-ended queue"""
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return self._size
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def is_empty(self) -> bool:
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"""Determine if the double-ended queue is empty"""
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return self._size == 0
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def index(self, i: int) -> int:
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"""Calculate circular array index"""
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# Implement circular array by modulo operation
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# When i exceeds the tail of the array, return to the head
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# When i exceeds the head of the array, return to the tail
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return (i + self.capacity()) % self.capacity()
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def push_first(self, num: int):
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"""Front enqueue"""
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if self._size == self.capacity():
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print("Double-ended queue is full")
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return
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# Move the front pointer one position to the left
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# Implement front crossing the head of the array to return to the tail by modulo operation
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self._front = self.index(self._front - 1)
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# Add num to the front
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self._nums[self._front] = num
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self._size += 1
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def push_last(self, num: int):
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"""Rear enqueue"""
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if self._size == self.capacity():
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print("Double-ended queue is full")
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return
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# Calculate rear pointer, pointing to rear index + 1
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rear = self.index(self._front + self._size)
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# Add num to the rear
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self._nums[rear] = num
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self._size += 1
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def pop_first(self) -> int:
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"""Front dequeue"""
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num = self.peek_first()
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# Move front pointer one position backward
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self._front = self.index(self._front + 1)
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self._size -= 1
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return num
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def pop_last(self) -> int:
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"""Rear dequeue"""
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num = self.peek_last()
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self._size -= 1
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return num
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def peek_first(self) -> int:
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"""Access front element"""
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if self.is_empty():
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raise IndexError("Double-ended queue is empty")
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return self._nums[self._front]
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def peek_last(self) -> int:
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"""Access rear element"""
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if self.is_empty():
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raise IndexError("Double-ended queue is empty")
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# Calculate rear element index
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last = self.index(self._front + self._size - 1)
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return self._nums[last]
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def to_array(self) -> list[int]:
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"""Return array for printing"""
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# Only convert elements within valid length range
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res = []
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for i in range(self._size):
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res.append(self._nums[self.index(self._front + i)])
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return res
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"""Driver Code"""
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if __name__ == "__main__":
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# Initialize double-ended queue
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deque = ArrayDeque(10)
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deque.push_last(3)
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deque.push_last(2)
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deque.push_last(5)
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print("Double-ended queue deque =", deque.to_array())
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# Access element
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peek_first: int = deque.peek_first()
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print("Front element peek_first =", peek_first)
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peek_last: int = deque.peek_last()
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print("Rear element peek_last =", peek_last)
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# Element enqueue
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deque.push_last(4)
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print("Element 4 rear enqueued, deque =", deque.to_array())
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deque.push_first(1)
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print("Element 1 front enqueued, deque =", deque.to_array())
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# Element dequeue
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pop_last: int = deque.pop_last()
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print("Rear dequeued element =", pop_last, ", deque after rear dequeue =", deque.to_array())
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pop_first: int = deque.pop_first()
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print("Front dequeued element =", pop_first, ", deque after front dequeue =", deque.to_array())
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# Get the length of the double-ended queue
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size: int = deque.size()
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print("Double-ended queue length size =", size)
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# Determine if the double-ended queue is empty
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is_empty: bool = deque.is_empty()
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print("Is the double-ended queue empty =", is_empty)
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