138.随机链表的复制（LeetCode）

深拷贝，是指将该链表除了正常单链表的数值和next指针拷贝，再将random指针进行拷贝

想法一

先拷贝出一份链表，再对于每个节点的random指针，在原链表进行遍历，找到random指针的指向，最后完成拷贝链表random的指向
时间复杂度：O(N^2)

想法二

下面这种方法，是使用C语言的最优解

时间复杂度：O(N)

完整代码如下：

struct Node* copyRandomList(struct Node* head)
{
	//1.拷贝节点插入原节点的后面
    struct Node* cur = head;

    while (cur)
    {
        struct Node* copy = (struct Node*)malloc(sizeof(struct Node));
        copy->val = cur->val;
        struct Node* next = cur->next;

        copy->next = next;
        cur->next = copy;
        cur = next;
    }
    //2.控制拷贝节点的random
    cur = head;

    while (cur)
    {
        struct Node* copy = cur->next;
        
        if (cur->random)
        {
            copy->random = cur->random->next;
        }
        else
        {
            copy->random = NULL;
        }
        cur = copy->next;
    }
    //3.拷贝节点解下来组成拷贝链表，恢复原链表
    cur = head;
    struct Node* copyHead = NULL;
    struct Node* copyTail = NULL;

    while (cur)
    {
        struct Node* copy = cur->next;
        struct Node* next = copy->next;

        if (copyTail)
        {
            copyTail->next = copy;
            copyTail = copyTail->next;
        }
        else
        {
            copyHead = copyTail = copy;
        }

        cur->next = next;
        cur = next;
    }

    return copyHead;
}