Linked List 구현

class Node:
     def __init__(self, value):
         self.value = value
         self.next = None

class LinkedList(object):
    def __init__(self):
        self.head = None
        self.tail = None

    def append(self, value):
        new_node = Node(value)
        if self.head is None:
            self.head = new_node
            self.tail = new_node
        else:
            self.tail.next = new_node
            self.tail = new_node

    def insert_at(self, idx, value):
        new_node = Node(value)
        ptr = self.head
        cnt = 0
        while ptr is not None and cnt < idx - 1:
            ptr = ptr.next
            cnt += 1
        new_node.next = ptr.next
        ptr.next = new_node

    def delete_at(self, idx):
        ptr = self.head
        cnt = 0
        while ptr is not None and cnt < idx - 1:
            ptr = ptr.next
            cnt += 1
        ptr.next = ptr.next.next

ll = LinkedList()

ll.append(1)
ll.append(2)
ll.append(3)
ll.append(4)
ll.append(5)
ll.insert_at(3, 9)

def print_list(ll):
    ptr = ll.head
    while ptr:
        print(ptr.value, end=' ')
        ptr = ptr.next
    print()

print_list(ll)

ll.delete_at(2)
print_list(ll)