题解 | 【模板】链表

# 可以使用简单的列表来做这个链表，但是失去了本身的链表的意思
class Node:
    def __init__(self,val):
        self.val = val
        self.next = None
class Listlink:
    def __init__(self):
        self.head = None
    def insert(self, x, y):
        node = Node(y)
        if self.head == None:
            node = Node(y)
            self.head = node
            return
        if self.head.val == x:
            node.next = self.head
            self.head = node
            return 
        
        pre = self.head
        cur = self.head.next
        while cur:
            if cur.val == x:
                pre.next = node
                node.next = cur
                return
            pre = cur
            cur = cur.next
        pre.next = node
    def delete(self,x):
        if self.head == None:
            return
        pre = self.head
        cur = pre.next
        if self.head.val == x:
            self.head = cur
            return 
        while cur:
            if cur.val == x:
                if cur.next == None:
                    pre.next = None
                    return
                pre.next = cur.next
                return
            pre = cur
            cur = cur.next
    def display(self):
        cur = self.head
        if cur == None:
            print("NULL")
            return
        while cur:
            print(cur.val,end = " ")
            cur = cur.next
if __name__ == "__main__":
    link = Listlink()
    n = int(input())
    for item in range(n):
        s = list(input().split())
        if s[0] == "insert":
            link.insert(int(s[1]),int(s[2]))
        elif s[0] == "delete":
            link.delete(int(s[1]))
    link.display()