Add array_deque.py and linkedlist_deque.py (krahets#399)

codes/python/chapter_stack_and_queue/array_deque.py

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+"""
+File: array_deque.py
+Created Time: 2023-03-01
+Author: Krahets ([email protected])
+"""
+
+import os.path as osp
+import sys
+
+sys.path.append(osp.dirname(osp.dirname(osp.abspath(__file__))))
+from include import *
+
+""" 基于环形数组实现的双向队列 """
+class ArrayDeque:
+    """  构造方法 """
+    def __init__(self, capacity):
+        self.nums = [0] * capacity
+        self.front = 0
+        self.que_size = 0
+
+    """  获取双向队列的容量  """
+    def capacity(self):
+        return len(self.nums)
+
+    """ 获取双向队列的长度  """
+    def size(self):
+        return self.que_size
+
+    """ 判断双向队列是否为空 """
+    def is_empty(self):
+        return self.que_size == 0
+
+    """ 计算环形数组索引 """
+    def index(self, i):
+        # 通过取余操作实现数组首尾相连
+        # 当 i 越过数组尾部后，回到头部
+        # 当 i 越过数组头部后，回到尾部
+        return (i + self.capacity()) % self.capacity()
+
+    """ 队首入队 """
+    def push_first(self, num):
+        if self.que_size == self.capacity():
+            print("双向队列已满")
+            return
+        # 队首指针向左移动一位
+        # 通过取余操作，实现 front 越过数组头部后回到尾部
+        self.front = self.index(self.front-1)
+        # 将 num 添加至队首
+        self.nums[self.front] = num
+        self.que_size += 1
+
+    """ 队尾入队 """
+    def push_last(self, num):
+        if self.que_size == self.capacity():
+            print("双向队列已满")
+            return
+        # 计算尾指针，指向队尾索引 + 1
+        rear = self.index(self.front + self.que_size)
+        # 将 num 添加至队尾
+        self.nums[rear] = num
+        self.que_size += 1
+
+    """ 队首出队 """
+    def poll_first(self):
+        num = self.peek_first()
+        # 队首指针向后移动一位
+        self.front = self.index(self.front+1)
+        self.que_size -= 1
+        return num
+
+    """ 队尾出队 """
+    def poll_last(self):
+        num = self.peek_last()
+        self.que_size -= 1
+        return num
+
+    """ 访问队首元素 """
+    def peek_first(self):
+        assert not self.is_empty(), "双向队列为空"
+        return self.nums[self.front]
+
+    """ 访问队尾元素 """
+    def peek_last(self):
+        assert not self.is_empty(), "双向队列为空"
+        # 计算尾元素索引
+        last = self.index(self.front + self.que_size - 1)
+        return self.nums[last]
+
+    """ 返回数组用于打印 """
+    def to_array(self):
+        # 仅转换有效长度范围内的列表元素
+        res = []
+        for i in range(self.que_size):
+            res.append(self.nums[self.index(self.front+i)])
+        return res
+
+
+""" Driver Code """
+if __name__ == "__main__":
+    """ 初始化双向队列 """
+    deque = ArrayDeque(10)
+    deque.push_last(3)
+    deque.push_last(2)
+    deque.push_last(5)
+    print("双向队列 deque =", deque.to_array())
+
+    """ 访问元素 """
+    peek_first = deque.peek_first()
+    print("队首元素 peek_first =", peek_first)
+    peek_last = deque.peek_last()
+    print("队尾元素 peek_last =", peek_last)
+
+    """ 元素入队 """
+    deque.push_last(4)
+    print("元素 4 队尾入队后 deque =", deque.to_array())
+    deque.push_first(1)
+    print("元素 1 队首入队后 deque =", deque.to_array())
+
+    """ 元素出队 """
+    poll_last = deque.poll_last()
+    print("队尾出队元素 =", poll_last, "，队尾出队后 deque =", deque.to_array())
+    poll_first = deque.poll_first()
+    print("队首出队元素 =", poll_first, "，队首出队后 deque =", deque.to_array())
+
+    """ 获取双向队列的长度 """
+    size = deque.size()
+    print("双向队列长度 size =", size)
+
+    """ 判断双向队列是否为空 """
+    is_empty = deque.is_empty()
+    print("双向队列是否为空 =", is_empty)

codes/python/chapter_stack_and_queue/linkedlist_deque.py

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+"""
+File: linkedlist_deque.py
+Created Time: 2023-03-01
+Author: Krahets ([email protected])
+"""
+
+import os.path as osp
+import sys
+
+sys.path.append(osp.dirname(osp.dirname(osp.abspath(__file__))))
+from include import *
+
+""" 双向链表结点 """
+class ListNode:
+    def __init__(self, val):
+        self.val = val
+        self.next = None  # 后继结点引用（指针）
+        self.prev = None  # 前驱结点引用（指针）
+
+""" 基于双向链表实现的双向队列 """
+class LinkedListDeque:
+    """ 构造方法 """
+    def __init__(self):
+        self.front, self.rear = None, None  # 头结点 front ，尾结点 rear
+        self.__size = 0  # 双向队列的长度
+
+    """ 获取双向队列的长度 """
+    def size(self):
+        return self.__size
+
+    """ 判断双向队列是否为空 """
+    def is_empty(self):
+        return self.size() == 0
+
+    """ 入队操作 """
+    def push(self, num, is_front):
+        node = ListNode(num)
+        # 若链表为空，则令 front, rear 都指向 node
+        if self.is_empty():
+            self.front = self.rear = node
+        # 队首入队操作
+        elif is_front:
+            # 将 node 添加至链表头部
+            self.front.prev = node
+            node.next = self.front
+            self.front = node  # 更新头结点
+        # 队尾入队操作
+        else:
+            # 将 node 添加至链表尾部
+            self.rear.next = node
+            node.prev = self.rear
+            self.rear = node  # 更新尾结点
+        self.__size += 1  # 更新队列长度
+
+    """ 队首入队 """
+    def push_first(self, num):
+        self.push(num, True)
+
+    """ 队尾入队 """
+    def push_last(self, num):
+        self.push(num, False)
+
+    """ 出队操作 """
+    def poll(self, is_front):
+        # 若队列为空，直接返回 None
+        if self.is_empty():
+            return None
+        # 队首出队操作
+        if is_front:
+            val = self.front.val  # 暂存头结点值
+            # 删除头结点
+            fnext = self.front.next
+            if fnext != None:
+                fnext.prev = None
+                self.front.next = None
+            self.front = fnext  # 更新头结点
+        # 队尾出队操作
+        else:
+            val = self.rear.val  # 暂存尾结点值
+            # 删除尾结点
+            rprev = self.rear.prev
+            if rprev != None:
+                rprev.next = None
+                self.rear.prev = None
+            self.rear = rprev  # 更新尾结点
+        self.__size -= 1  # 更新队列长度
+        return val
+
+    """ 队首出队 """
+    def poll_first(self):
+        return self.poll(True)
+
+    """ 队尾出队 """
+    def poll_last(self):
+        return self.poll(False)
+
+    """ 访问队首元素 """
+    def peek_first(self):
+        return None if self.is_empty() else self.front.val
+
+    """ 访问队尾元素 """
+    def peek_last(self):
+        return None if self.is_empty() else self.rear.val
+
+    """ 返回数组用于打印 """
+    def to_array(self):
+        node = self.front
+        res = [0] * self.size()
+        for i in range(self.size()):
+            res[i] = node.val
+            node = node.next
+        return res
+
+
+""" Driver Code """
+if __name__ == "__main__":
+    """ 初始化双向队列 """
+    deque = LinkedListDeque()
+    deque.push_last(3)
+    deque.push_last(2)
+    deque.push_last(5)
+    print("双向队列 deque =", deque.to_array())
+
+    """ 访问元素 """
+    peek_first = deque.peek_first()
+    print("队首元素 peek_first =", peek_first)
+    peek_last = deque.peek_last()
+    print("队尾元素 peek_last =", peek_last)
+
+    """ 元素入队 """
+    deque.push_last(4)
+    print("元素 4 队尾入队后 deque =", deque.to_array())
+    deque.push_first(1)
+    print("元素 1 队首入队后 deque =", deque.to_array())
+
+    """ 元素出队 """
+    poll_last = deque.poll_last()
+    print("队尾出队元素 =", poll_last, "，队尾出队后 deque =", deque.to_array())
+    poll_first = deque.poll_first()
+    print("队首出队元素 =", poll_first, "，队首出队后 deque =", deque.to_array())
+
+    """ 获取双向队列的长度 """
+    size = deque.size()
+    print("双向队列长度 size =", size)
+
+    """ 判断双向队列是否为空 """
+    is_empty = deque.is_empty()
+    print("双向队列是否为空 =", is_empty)