## Description

A linked list is given such that each node contains an additional random pointer which could point to any node in the list or null.

Return a deep copy of the list.

The Linked List is represented in the input/output as a list of n nodes. Each node is represented as a pair of [val, random_index] where:

• val: an integer representing Node.val
• random_index: the index of the node (range from 0 to n-1) where random pointer points to, or null if it does not point to any node.

Example 1: Input: head = [[7,null],[13,0],[11,4],[10,2],[1,0]]
Output: [[7,null],[13,0],[11,4],[10,2],[1,0]]


Example 2: Input: head = [[1,1],[2,1]]
Output: [[1,1],[2,1]]


Example 3: Input: head = [[3,null],[3,0],[3,null]]
Output: [[3,null],[3,0],[3,null]]


Example 4:

Input: head = []
Output: []
Explanation: Given linked list is empty (null pointer), so return null.


Constraints:

• -10000 <= Node.val <= 10000
• Node.random is null or pointing to a node in the linked list.
• Number of Nodes will not exceed 1000.

## Solutions

### 1. Copy same

# Time: O(n)
# Space: O(1)
"""
# Definition for a Node.
class Node:
def __init__(self, x: int, next: 'Node' = None, random: 'Node' = None):
self.val = int(x)
self.next = next
self.random = random
"""
class Solution:
def copyRandomList(self, head: 'Node') -> 'Node':
return
# copy nodes
while cur:
nxt = cur.next
cur.next = Node(cur.val, cur.next, cur.random)
cur.next.next = nxt
cur = nxt
# copy random pointers
while cur:
if cur.random:
cur.next.random = cur.random.next
cur = cur.next.next
# separate two parts