[PROD]スタックの使用

📌 Stack

class Stack:
    def __init__(self):
        self.len = 0
        self.list = []
        
    def push(self, num):
        self.list.append(num)
        self.len += 1
    
    def pop(self):
        if self.size() == 0:
            return -1
        pop_result = self.list[self.len - 1]
        del self.list[self.len - 1]
        self.len -= 1
        return pop_result
        
    def size(self):
        return self.len
        
    def empty(self):
        return 1 if self.len == 0 else 0
        
    def top(self):
        return self.list[-1] if self.size() != 0 else -1

📌 List

 //stack = [3, 4, 5]
 stack.append(6)
 stack.append(7)
// stack [3, 4, 5, 6, 7]
 stack.pop()  //7
 //stack [3, 4, 5, 6]
 stack.pop()   //6
 stack.pop()   //5
// stack [3, 4]