题解 | 【模板】栈的操作

class Stack:
    def __init__(self) -> None:
        self.items = []
    def push(self,x):
        self.items.append(x)
    def pop(self):
        if self.items:
            self.items.pop()
        else:
            print("Empty")
    def query(self):
        if self.items:
            print(self.items[-1])
        else:
            print("Empty")
    def size(self):
        print(len(self.items))


n = int(input())
stack = Stack()

for _ in range(n):
    commend = input().strip().split()
    if commend[0] == "push":
        stack.push(commend[1])
    elif commend[0] == "size":
        stack.size()
    elif commend[0] == "query":
        stack.query()
    elif commend[0] == "pop":
        stack.pop()