题解 | 【模板】栈的操作

import sys
def main():
    lines = sys.stdin.read().splitlines()
    n = int(lines[0])
    stack = []
    for line in lines[1:n+1]:
        parts = line.strip().split()
        op = parts [0]
        if op == 'push':
            x = int(parts[1]) 
            stack.append(x)
        elif op == 'pop':
            if not stack:
                print("Empty")
            else:
                stack.pop()
        elif op == 'query':
            if not stack:
                print("Empty")
            else:
                print(stack[-1])
        elif op == 'size':
            print(len(stack))
if __name__=="__main__":
    main()