【C++做题练习】复制带随机指针的链表（力扣No.138）

Leetcode 138题解题

https://leetcode-cn.com/problems/copy-list-with-random-pointer/
给你一个长度为 n 的链表，每个节点包含一个额外增加的随机指针 random ，该指针可以指向链表中的任何节点或空节点。构造这个链表的 深拷贝。返回复制链表的头节点。

解题思路：

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

struct Node* copyRandomList(struct Node* head) {
    if(head == NULL){
        return NULL;
    }
	struct Node* cur = head;
    while(cur){
        struct Node* copy = (struct Node*)malloc(sizeof(struct Node));
        copy->val = cur->val;
        copy->next = cur->next;
        cur->next = copy;
        cur = copy->next;
    }
    cur = head;
    while(cur){
        struct Node *copy = cur->next;
        if(cur->random != NULL){
            copy->random = cur->random->next;
        }else{
            copy->random = NULL;
        } 
        cur = copy->next;   
    }
    struct Node *newlist = (struct Node*)malloc(sizeof(struct Node));
    newlist->next = NULL;
    struct Node *tail = newlist;
    cur = head;
    struct Node *copy;
    struct Node* tmp;
    while(cur){
        copy = cur->next;
        tmp = copy->next;
        copy->next = tail->next;
        tail->next = copy;
        tail = copy;
        cur->next = tmp;
        cur = tmp;
    }
    struct Node *ret = newlist->next;
    free(newlist);
    newlist->next = NULL;
    return ret;
}