《剑指Offer（第二版）》面试题35. 复杂链表的复制

请实现 copyRandomList 函数，复制一个复杂链表。在复杂链表中，每个节点除了有一个 next 指针指向下一个节点，还有一个 random 指针指向链表中的任意节点或者 null。

示例 1：
输入：head = [[7,null],[13,0],[11,4],[10,2],[1,0]]
输出：[[7,null],[13,0],[11,4],[10,2],[1,0]]

示例 2：
输入：head = [[1,1],[2,1]]
输出：[[1,1],[2,1]]

示例 3：
输入：head = [[3,null],[3,0],[3,null]]
输出：[[3,null],[3,0],[3,null]]

示例 4：
输入：head = []
输出：[]
解释：给定的链表为空（空指针），因此返回 null。
 
提示：
-10000 <= Node.val <= 10000
Node.random 为空（null）或指向链表中的节点。
节点数目不超过 1000 。

理解题意：链表的深拷贝
HASH法：时间O(N),空间O(N)

"""
# 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':
        if head == None:
            return None

        org = []
        res = []
        new_head = Node(head.val)

        org.append(head)
        res.append(new_head)
        head = head.next

        while head != None:
            new = Node(head.val)
            org.append(head)
            res.append(new)
            head = head.next
            
        for i in range(len(org)):
            if org[i].next != None:
                res[i].next = res[org.index(org[i].next)]
            else:
                res[i].next = None
            if org[i].random != None:
                res[i].random = res[org.index(org[i].random)]
            else:
                res[i].random = None
            
        return new_head

不适用额外空间，在原链表添加节点   时间O(N),空间0(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':
        if head == None:
            return None

        cur = head

        while cur != None:  # 添加新节点
            new = Node(cur.val)
            new.next = cur.next
            cur.next = new
            cur = new.next
        
        cur = head
        while cur:  # 设置random
            cur.next.random = cur.random.next if cur.random else None
            cur = cur.next.next
        
        new_head = cur = head.next
        while cur:  # 去除新链表
            cur.next = cur.next.next if cur.next else None
            cur = cur.next
            
        return new_head