[] 20. Offer a stack wins the min function implementation comprises python

Title Description

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Stack data structure definition, implement this type can be a min function smallest elements contained in the stack (should the time complexity O (1)).

Problem-solving ideas

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Stack comprising the min function
push stack, pop, min operation time complexity is O (1)
using aAuxiliary stackSave a minimum

Code

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# -*- coding:utf-8 -*-
class Solution:
    def __init__(self):
        self.stack = []
        self.minval = []
         
    def push(self, node):
    	self.stack.append(node)
        min = self.min()  # 使用一个辅助栈来保存最小值
        if min and min < node:
            self.minval.append(min)
        else:
            self.minval.append(node)
         
    def pop(self):
        if self.stack:
            self.minval.pop()
            return self.stack.pop()
        return None
     
    def top(self):
        # write code here
        if self.stack:
            return self.stack[-1]
         
    def min(self):
        # write code here
        if self.minval:
            return self.minval[-1]

if __name__ == '__main__':
    s = Solution()
    s.push(7)
    s.push(6)
    s.push(3)
    s.pop()
    s.push(2)
    print(s.stack)
    print(s.min())

Output Example

[7,6,2]
2