欢迎fork and star：Nowcoder-Repository-github

138. Copy List with Random Pointer

题目

 A linked list is given such that each node contains an additional random pointer which could point to any node in the list or null.

Return a deep copy of the list. 

解析

• 思路参考;LeetCode:Copy List with Random Pointer

1. 在原链表的每个节点后面拷贝出一个新的节点

2. 依次给新的节点的随机指针赋值，而且这个赋值非常容易 cur->next->random = cur->random->next

3. 断开链表可得到深度拷贝后的新链表

• 几个易错点：

• 插入在当前节点前或者后要分清
• copy random 指针->next理解，就是当前copy节点的random节点指向当前cur节点的random节点的下一个节点

• 分离链表是否加头结点，不加也可以吧，指针分离都要连起来

/**
 * Definition for singly-linked list with a random pointer.
 * struct RandomListNode {
 *     int label;
 *     RandomListNode *next, *random;
 *     RandomListNode(int x) : label(x), next(NULL), random(NULL) {}
 * };
 */

class Solution {
public:
    RandomListNode *copyRandomList(RandomListNode *head) {

        if (!head)
            return NULL;
        //if (!head->next) //bug: 这句话bug,不加才行！！！
        //{
        //  RandomListNode* copy = new RandomListNode(head->label);
        //  return copy;
        //}

        RandomListNode* cur = head;

        RandomListNode* temp = NULL;
        while (cur) //在每个节点后面copy节点
        {
            RandomListNode* newNode = new RandomListNode(cur->label); //bug 在之后插入

            temp = cur->next;
            cur->next = newNode;
            newNode->next = temp;
            
            cur = cur->next->next;
        }

        //每个节点copy random指针

        cur = head;
        while (cur) //bug 指针越界
        {
            if (cur->random)
            {
                cur->next->random = cur->random->next; //??->next
            }
            cur=cur->next->next;
        }

        // 将original list和copy list分开

        cur = head;
        RandomListNode* copyHead = new RandomListNode(0);
        RandomListNode* copy_cur = copyHead;

        RandomListNode* next = NULL;
        while (cur)
        {
            next = cur->next->next;

            copy_cur->next = cur->next;
            copy_cur = cur->next;

            cur->next = next;
            cur = next;

        }

        return copyHead->next;

        /*RandomListNode*p = NULL;
        p = head;
        RandomListNode* res = head->next;
        while (p->next != NULL)
        {
            RandomListNode* tmp = p->next;
            p->next = p->next->next;
            p = tmp;
        }
        return res; */
    }
};

题目来源

• 138. Copy List with Random Pointer