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"""
https://leetcode.com/problems/design-linked-list/
Design your implementation of the linked list. You can choose to use a singly or doubly linked list.
A node in a singly linked list should have two attributes: val and next. val is the value of the current node, and next is a pointer/reference to the next node.
If you want to use the doubly linked list, you will need one more attribute prev to indicate the previous node in the linked list. Assume all nodes in the linked list are 0-indexed.
Implement the MyLinkedList class:
MyLinkedList() Initializes the MyLinkedList object.
int get(int index) Get the value of the indexth node in the linked list. If the index is invalid, return -1.
void addAtHead(int val) Add a node of value val before the first element of the linked list. After the insertion, the new node will be the first node of the linked list.
void addAtTail(int val) Append a node of value val as the last element of the linked list.
void addAtIndex(int index, int val) Add a node of value val before the indexth node in the linked list. If index equals the length of the linked list, the node will be appended to the end of the linked list. If index is greater than the length, the node will not be inserted.
void deleteAtIndex(int index) Delete the indexth node in the linked list, if the index is valid.
Example 1:
Input
["MyLinkedList", "addAtHead", "addAtTail", "addAtIndex", "get", "deleteAtIndex", "get"]
[[], [1], [3], [1, 2], [1], [1], [1]]
Output
[null, null, null, null, 2, null, 3]
Explanation
MyLinkedList myLinkedList = new MyLinkedList();
myLinkedList.addAtHead(1);
myLinkedList.addAtTail(3);
myLinkedList.addAtIndex(1, 2); // linked list becomes 1->2->3
myLinkedList.get(1); // return 2
myLinkedList.deleteAtIndex(1); // now the linked list is 1->3
myLinkedList.get(1); // return 3
Constraints:
0 <= index, val <= 1000
Please do not use the built-in LinkedList library.
At most 2000 calls will be made to get, addAtHead, addAtTail, addAtIndex and deleteAtIndex.
"""
from Common.Constants import null
from Common.ObjectTestingUtils import run_object_tests
# Runtime: 152 ms, faster than 86.25% of Python3 online submissions for Design Linked List.
# Memory Usage: 15.2 MB, less than 26.97% of Python3 online submissions for Design Linked List.
class MyLinkedList:
class Node:
def __init__(self, val, next = None):
self.val = val
self.next = next
# def print(self):
# node = self.head
# while node:
# print(node.val, flush=True, sep=' ', end=' ')
# node = node.next
# print()
def __init__(self):
self.head = None
self.last = None
self.count = 0
def get(self, index: int) -> int:
if not self.head:
return -1
result = self.head
for i in range(index):
result = result.next
if not result:
return -1
return result.val
def addAtHead(self, val: int) -> None:
self.head = self.Node(val, self.head)
if not self.last:
self.last = self.head
self.count += 1
# self.print()
def addAtTail(self, val: int) -> None:
if not self.head:
return self.addAtHead(val)
self.last.next = self.Node(val)
self.last = self.last.next
self.count += 1
# self.print()
def addAtIndex(self, index: int, val: int) -> None:
if index < 0 or index > self.count:
return
if index == self.count:
return self.addAtTail(val)
prev, curr = None, self.head
for i in range(index):
prev, curr = curr, curr.next
if not prev:
return self.addAtHead(val)
prev.next = self.Node(val, curr)
self.count += 1
# self.print()
def deleteAtIndex(self, index: int) -> None:
if index < 0 or index >= self.count:
return
prev, curr = None, self.head
for i in range(index):
prev, curr = curr, curr.next
if not prev:
self.head = self.head.next
if not self.head:
self.last = None
self.count -= 1
return
if not curr.next:
self.last = prev
prev.next = curr.next
self.count -= 1
# self.print()
# Your MyLinkedList object will be instantiated and called as such:
# obj = MyLinkedList()
# param_1 = obj.get(index)
# obj.addAtHead(val)
# obj.addAtTail(val)
# obj.addAtIndex(index,val)
# obj.deleteAtIndex(index)
tests = [
[
["MyLinkedList", "addAtHead", "addAtTail", "addAtIndex", "get", "deleteAtIndex", "get"],
[[], [1], [3], [1, 2], [1], [1], [1]],
[null, null, null, null, 2, null, 3]
],
[
["MyLinkedList","addAtHead","addAtHead","addAtHead","addAtIndex","deleteAtIndex","addAtHead","addAtTail","get","addAtHead","addAtIndex","addAtHead"],
[[],[7],[2],[1],[3,0],[2],[6],[4],[4],[4],[5,0],[6]],
[null,null,null,null,null,null,null,null,4,null,null,null]
]
# 6 1 2 4
]
run_object_tests(tests, cls=MyLinkedList, debug=False)