python栈与队列

python栈与队列

• 栈的实现

  class Stack(object):
      """栈"""
  
      def __init__(self):
          self.__item = []
  
      def push(self,item):
          """添加一个新的元素item到栈顶"""
          self.__item.append(item)
  
      def pop(self):
          """弹出栈顶元素"""
          return self.__item.pop()
  
  
      def peek(self):
          """返回栈顶元素"""
          if self.__item:
              return self.__item[-1]
          else:
              return None
  
      def is_empty(self):
          """判断栈是否为空"""
          return self.__item == []
  
      def size(self):
          """返回栈的元素个数"""
          return len(self.__item)
  
  
  if __name__ == "__main__":
      stack = Stack()
      stack.push("hello")
      stack.push("world")
      stack.push("itcast")
      print(stack.size())
      print(stack.peek())
      print(stack.pop())
      print(stack.pop())
      print(stack.pop())
  
  # 运行结果
  3
  itcast
  itcast
  world
  hello
  

• 队列实现

  class Queue(object):
      """队列"""
      
      def __init__(self):
          self.__item = []
  
      def enqueue(self,item):
          """往队列中添加一个item元素"""
          self.__item.insert(0,item)
  
      def dequeue(self):
          """从队列头部删除一个元素"""
          if self.__item:
              return self.__item.pop()
          else:
              return None
  
      def is_empty(self):
          """判断一个队列是否为空"""
          return self.__item == []
  
      def size(self):
          """返回队列的大小"""
          return len(self.__item)
  
  
  if __name__ == "__main__":
      q = Queue()
      q.enqueue("hello")
      q.enqueue("world")
      q.enqueue("itcast")
      print(q.size())
      print(q.dequeue())
      print(q.dequeue())
      print(q.dequeue())
      
      
  # 运行结果
  3
  hello
  world
  itcast
  

• 双端队列

  class Deque(object):
      """双端队列"""
  
      def __init__(self):
          self.__item = []
  
      def add_front(self,item):
          """从队头加入一个item元素"""
          self.__item.insert(0,item)
  
      def add_rear(self,item):
          """从队尾加入一个item元素"""
          self.__item.append(item)
  
      def remove_front(self):
          """从队头删除一个item元素"""
          if self.__item:
              return self.__item.pop(0)
          else:
              return None
  
      def remove_rear(self):
          """从队尾删除一个item元素"""
          if self.__item:
              return self.__item.pop()
          else:
              return None
  
      def is_empty(self):
          """判断双端队列是否为空"""
          return self.__item == []
  
      def size(self):
          """返回队列的大小"""
          return len(self.__item)
  
  
  
  
  if __name__ == "__main__":
      deque = Deque()
      deque.add_front(1)
      deque.add_front(2)
      deque.add_rear(3)
      deque.add_rear(4)
      print(deque.size())
      print(deque.remove_front())
      print(deque.remove_front())
      print(deque.remove_rear())
      print(deque.remove_rear())
    
    
  # 运行结果
  4
  2
  1
  4
  3