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Add array_deque.py and linkedlist_deque.py (#399)
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Yudong Jin
GitHub
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131
codes/python/chapter_stack_and_queue/array_deque.py
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131
codes/python/chapter_stack_and_queue/array_deque.py
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"""
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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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import os.path as osp
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import sys
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sys.path.append(osp.dirname(osp.dirname(osp.abspath(__file__))))
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from include import *
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""" 基于环形数组实现的双向队列 """
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class ArrayDeque:
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""" 构造方法 """
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def __init__(self, capacity):
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self.nums = [0] * capacity
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self.front = 0
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self.que_size = 0
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""" 获取双向队列的容量 """
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def capacity(self):
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return len(self.nums)
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""" 获取双向队列的长度 """
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def size(self):
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return self.que_size
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""" 判断双向队列是否为空 """
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def is_empty(self):
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return self.que_size == 0
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""" 计算环形数组索引 """
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def index(self, i):
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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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""" 队首入队 """
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def push_first(self, num):
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if self.que_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.que_size += 1
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""" 队尾入队 """
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def push_last(self, num):
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if self.que_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.que_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.que_size += 1
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""" 队首出队 """
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def poll_first(self):
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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.que_size -= 1
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return num
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""" 队尾出队 """
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def poll_last(self):
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num = self.peek_last()
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self.que_size -= 1
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return num
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""" 访问队首元素 """
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def peek_first(self):
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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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""" 访问队尾元素 """
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def peek_last(self):
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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.que_size - 1)
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return self.nums[last]
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""" 返回数组用于打印 """
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def to_array(self):
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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.que_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 = deque.peek_first()
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print("队首元素 peek_first =", peek_first)
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peek_last = 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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poll_last = deque.poll_last()
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print("队尾出队元素 =", poll_last, "，队尾出队后 deque =", deque.to_array())
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poll_first = deque.poll_first()
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print("队首出队元素 =", poll_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 = 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 = deque.is_empty()
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print("双向队列是否为空 =", is_empty)
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148
codes/python/chapter_stack_and_queue/linkedlist_deque.py
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codes/python/chapter_stack_and_queue/linkedlist_deque.py
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"""
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File: linkedlist_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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import os.path as osp
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import sys
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sys.path.append(osp.dirname(osp.dirname(osp.abspath(__file__))))
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from include import *
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""" 双向链表结点 """
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class ListNode:
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def __init__(self, val):
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self.val = val
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self.next = None # 后继结点引用（指针）
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self.prev = None # 前驱结点引用（指针）
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""" 基于双向链表实现的双向队列 """
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class LinkedListDeque:
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""" 构造方法 """
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def __init__(self):
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self.front, self.rear = None, None # 头结点 front ，尾结点 rear
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self.__size = 0 # 双向队列的长度
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""" 获取双向队列的长度 """
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def size(self):
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return self.__size
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""" 判断双向队列是否为空 """
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def is_empty(self):
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return self.size() == 0
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""" 入队操作 """
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def push(self, num, is_front):
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node = ListNode(num)
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# 若链表为空，则令 front, rear 都指向 node
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if self.is_empty():
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self.front = self.rear = node
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# 队首入队操作
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elif is_front:
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# 将 node 添加至链表头部
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self.front.prev = node
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node.next = self.front
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self.front = node # 更新头结点
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# 队尾入队操作
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else:
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# 将 node 添加至链表尾部
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self.rear.next = node
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node.prev = self.rear
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self.rear = node # 更新尾结点
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self.__size += 1 # 更新队列长度
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""" 队首入队 """
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def push_first(self, num):
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self.push(num, True)
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""" 队尾入队 """
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def push_last(self, num):
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self.push(num, False)
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""" 出队操作 """
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def poll(self, is_front):
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# 若队列为空，直接返回 None
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if self.is_empty():
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return None
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# 队首出队操作
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if is_front:
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val = self.front.val # 暂存头结点值
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# 删除头结点
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fnext = self.front.next
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if fnext != None:
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fnext.prev = None
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self.front.next = None
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self.front = fnext # 更新头结点
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# 队尾出队操作
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else:
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val = self.rear.val # 暂存尾结点值
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# 删除尾结点
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rprev = self.rear.prev
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if rprev != None:
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rprev.next = None
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self.rear.prev = None
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self.rear = rprev # 更新尾结点
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self.__size -= 1 # 更新队列长度
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return val
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""" 队首出队 """
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def poll_first(self):
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return self.poll(True)
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""" 队尾出队 """
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def poll_last(self):
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return self.poll(False)
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""" 访问队首元素 """
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def peek_first(self):
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return None if self.is_empty() else self.front.val
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""" 访问队尾元素 """
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def peek_last(self):
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return None if self.is_empty() else self.rear.val
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""" 返回数组用于打印 """
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def to_array(self):
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node = self.front
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res = [0] * self.size()
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for i in range(self.size()):
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res[i] = node.val
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node = node.next
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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 = LinkedListDeque()
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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 = deque.peek_first()
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print("队首元素 peek_first =", peek_first)
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peek_last = 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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poll_last = deque.poll_last()
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print("队尾出队元素 =", poll_last, "，队尾出队后 deque =", deque.to_array())
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poll_first = deque.poll_first()
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print("队首出队元素 =", poll_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 = 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 = deque.is_empty()
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print("双向队列是否为空 =", is_empty)
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