题解 | #【模板】链表#

class linkedlist:
    def __init__(self):
        self.items = []
    
    def insert(self, x, y):
        if x in self.items:
            loc = self.items.index(x)
            self.items.insert(loc, y)
        else:
            self.items.append(y)
            
    def delete(self, x):
        if x in self.items:
            loc = self.items.index(x)
            self.items.pop(loc)
    
    def size(self):
        return len(self.items)
    
    def taverlse(self):
        for i in range(len(self.items)):
            print(self.items[i], end = " ")

s = linkedlist()
n = int(input())
for i in range(n):
    message = input()
    messagesplt = message.split(" ")
    if messagesplt[0] == 'insert':
        a = messagesplt[1]
        b = messagesplt[2]
        s.insert(a, b)
    elif messagesplt[0] == 'delete':
        a = messagesplt[1]
        s.delete(a)
    else:
        raise ValueError("无此操作")
if s.size() == 0:
    print("NULL")
else:
    s.taverlse()