/**
 * Definition for a Node.
 * struct Node {
 *     int val;
 *     struct Node *next;
 *     struct Node *random;
 * };
 */

typedef struct Node Node;
struct Node* copyRandomList(struct Node* head) {
    if(head==NULL)
        return NULL;
    //1.拷贝结点，连接到原结点的后面
    Node*cur=head;
    while(cur){
        Node*copy=(Node*)malloc(sizeof(Node));
        copy->next=NULL;
        copy->random=NULL;
        copy->val=cur->val;
        // //相当于插入
        // copy->next=cur->next;
        // cur->next=copy;
        Node*next=cur->next;
        cur->next=copy;
        copy->next=next;

        cur=next;
    }

    //2.处理拷贝结点的random
    cur=head;
    while(cur){
        Node*copy=cur->next;
        if(cur->random)
            copy->random=cur->random->next;
        else
            copy->random=NULL;
        cur=cur->next->next;
    }

    //3.拆
    cur=head;
    Node*copyHead=head->next;//因为函数最后返回的是头指针
    while(cur){
        Node*copy=cur->next;
        Node*next=cur->next->next;

        cur->next=next;
        if(next)
            copy->next=next->next;
        else
            copy->next=NULL;
        cur=next;
    }
    return copyHead;
}