Copy List with Random Pointer

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.

参考：深度拷贝，浅度拷贝，Lazy拷贝解析http://www.2cto.com/kf/201401/276086.html

思路： Step 1: 首先指向在原链表的每个节点后面，复制一个新的节点，原链表长度变为 2 倍

random 指针指向的是 原链表节点 random 指针指向的节点的后面的那个节点

Step 2: 将链表拆成两个 lists

 

C++实现代码：

#include<iostream>

#include<new>

using namespace std;





// 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==NULL)

            return NULL;

        RandomListNode *p=head;

        while(p)

        {

            RandomListNode *q=new RandomListNode(p->label);

            q->next=p->next;

            p->next=q;

            p=q->next;

        }

        p=head;

        while(p)

        {

            if(p->random)

                p->next->random=p->random->next;

            p=p->next->next;

        }

        RandomListNode *retHead = NULL;

        RandomListNode *tRet = NULL;

        p = head;

        while(p)

        {

            if(retHead == NULL)

            {

                retHead = p->next;

                tRet = retHead;

                p->next = p->next->next;

                p = p->next;

            }

            else

            {

                tRet->next = p->next;

                p->next = p->next->next;

                p = p->next;

                tRet = tRet->next;

            }

        }

        return retHead;

    }

    void createList(RandomListNode *&head)

    {

        RandomListNode *p=NULL;

        int i=0;

        int arr[10]= {10,9,8,7,6,5,4,3,2,1};

        for(i=0; i<10; i++)

        {

            if(head==NULL)

            {

                head=new RandomListNode(arr[i]);

                if(head==NULL)

                    return;

            }

            else

            {

                p=new RandomListNode(arr[i]);

                p->next=head;

                head=p;

            }

        }

    }

};



int main()

{

    Solution s;

    RandomListNode *L=NULL;

    s.createList(L);

    RandomListNode *L2=s.copyRandomList(L);

    RandomListNode *p=L2;

    while(p)

    {

        cout<<p->label<<" ";

        p=p->next;

    }

}