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HomeBackend DevelopmentPython TutorialPython实现包含min函数的栈

本文实例讲述了Python实现包含min函数的栈。分享给大家供大家参考,具体如下:

# coding=utf8
'''
题目:定义栈的数据结构,请在该类型中实现一个能够得到栈的最小元素的min函数。
在该栈中,调用min、push及pop的时间复杂度都是O(1)。
'''
class Stack():
  def __init__(self):
    self.main_stack = []
    # 辅助栈,每次次最小的元素压入辅助栈
    self.assist_stack = []
    # 记录栈中的最小元素
    self._min = None
  def min(self):
    return self._min
  def push(self, data):
    self.main_stack.append(data)
    if self._min is None:
      self._min = data
    else:
      if data < self._min:
        self._min = data
    # 将最小的元素压入辅助栈
    self.assist_stack.append(self._min)
  def pop(self):
    if len(self.main_stack) == 0:
      raise Exception('no data')
    elif len(self.main_stack) == 1:
      self.assist_stack.pop()
      self._min = None
      return self.main_stack.pop()
    else:
      self.assist_stack.pop()
      self._min = self.assist_stack[-1]
      return self.main_stack.pop()
if __name__ == '__main__':
  s = Stack()
  s.push(3)
  s.push(4)
  s.push(2)
  s.push(1)
  print s.min()
  s.pop()
  s.pop()
  print s.min()
  s.pop()
  print s.min()
  s.pop()
  print s.min()
  s.pop()

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希望本文所述对大家Python程序设计有所帮助。

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