leetcode_138 Copy List with Random Pointer

class Solution
{
public:
RandomListNode *copyRandomList(RandomListNode *head)
{
if (head == NULL)
return NULL;
// 步骤1：复制节点，并将复制后的节点插入到原节点的后面
RandomListNode *pos1 = head, *pos2 = head->next;
while (pos1 != NULL)
{
pos1->next = new RandomListNode(pos1->label);
pos1->next->next = pos2;
pos1 = pos2;
if (pos2 != NULL)
pos2 = pos2->next;
}
// 步骤2：更新所有复制的节点的random节点，即h.next.random = h.random.next
pos1 = head;
pos2 = head->next;
while (pos1 != NULL)
{
if (pos1->random == NULL)
pos2->random = NULL;
else
pos2->random = pos1->random->next;
pos1 = pos1->next->next;
if (pos2->next != NULL)
pos2 = pos2->next->next;
}
// 步骤3：将原链表与复制的链表断开
RandomListNode *res = head->next;
pos1 = head;
pos2 = head->next;
while (pos1->next != NULL)
{
pos1->next = pos2->next;
pos1 = pos2;
if (pos2->next != NULL)
pos2 = pos2->next;
}
pos1->next = NULL;
pos2->next = NULL;
return res;
}
}

public RandomListNode copyRandomList2(RandomListNode head) {
if (head == null)
return null;
// 遍历链表，复制节点，并将复制的节点放到原节点的后面
RandomListNode h = head;
while (h != null) {
RandomListNode copy = new RandomListNode(h.label);
RandomListNode next = h.next;
h.next = copy;
copy.next = next;
h = next;
}
// 遍历链表，更改链表的random节点
h = head;
while (h != null) {
if (h.random != null) {
h.next.random = h.random.next;
}
h = h.next.next;
}
// 遍历节点，将原链表与复制链表断开
h = head;
RandomListNode newHead = h.next;
while (h != null) {
RandomListNode copy = h.next;
h.next = copy.next;
h = h.next;
copy.next = h != null ? h.next : null;
}
return newHead;
}