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127 lines
3.8 KiB
Python
127 lines
3.8 KiB
Python
"""
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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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"""基于环形数组实现的双向队列"""
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def __init__(self, capacity: int) -> None:
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"""构造方法"""
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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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"""获取双向队列的容量"""
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return len(self.__nums)
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def size(self) -> int:
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"""获取双向队列的长度"""
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return self.__size
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def is_empty(self) -> bool:
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"""判断双向队列是否为空"""
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return self.__size == 0
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def index(self, i: int) -> int:
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"""计算环形数组索引"""
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# 通过取余操作实现数组首尾相连
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# 当 i 越过数组尾部后，回到头部
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# 当 i 越过数组头部后，回到尾部
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return (i + self.capacity()) % self.capacity()
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def push_first(self, num: int) -> None:
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"""队首入队"""
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if self.__size == self.capacity():
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print("双向队列已满")
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return
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# 队首指针向左移动一位
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# 通过取余操作，实现 front 越过数组头部后回到尾部
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self.__front = self.index(self.__front - 1)
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# 将 num 添加至队首
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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) -> None:
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"""队尾入队"""
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if self.__size == self.capacity():
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print("双向队列已满")
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return
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# 计算尾指针，指向队尾索引 + 1
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rear = self.index(self.__front + self.__size)
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# 将 num 添加至队尾
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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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"""队首出队"""
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num = self.peek_first()
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# 队首指针向后移动一位
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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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"""队尾出队"""
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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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"""访问队首元素"""
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assert not self.is_empty(), "双向队列为空"
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return self.__nums[self.__front]
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def peek_last(self) -> int:
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"""访问队尾元素"""
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assert not self.is_empty(), "双向队列为空"
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# 计算尾元素索引
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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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"""返回数组用于打印"""
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# 仅转换有效长度范围内的列表元素
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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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# 初始化双向队列
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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("双向队列 deque =", deque.to_array())
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# 访问元素
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peek_first: int = deque.peek_first()
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print("队首元素 peek_first =", peek_first)
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peek_last: int = deque.peek_last()
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print("队尾元素 peek_last =", peek_last)
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# 元素入队
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deque.push_last(4)
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print("元素 4 队尾入队后 deque =", deque.to_array())
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deque.push_first(1)
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print("元素 1 队首入队后 deque =", deque.to_array())
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# 元素出队
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pop_last: int = deque.pop_last()
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print("队尾出队元素 =", pop_last, "，队尾出队后 deque =", deque.to_array())
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pop_first: int = deque.pop_first()
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print("队首出队元素 =", pop_first, "，队首出队后 deque =", deque.to_array())
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# 获取双向队列的长度
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size: int = deque.size()
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print("双向队列长度 size =", size)
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# 判断双向队列是否为空
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is_empty: bool = deque.is_empty()
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print("双向队列是否为空 =", is_empty)
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