leetcode 138. Copy List with Random Pointer 链表复制 + HashMap

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.

本题题意就是复制链表，注意使用HashMap等结构保存相关信息，这样更加方便。

代码如下：

import java.util.HashMap;import java.util.Map;/*class RandomListNode {      int label;      RandomListNode next, random;      RandomListNode(int x) { this.label = x; }};*//* *  这个是用一个map映射关系来获取相关的信息，这样避免了直接复制的遍历开销 * */public class Solution{     public RandomListNode copyRandomList(RandomListNode head)      {            if(head == null)                return head;            Map<Integer, RandomListNode> map = new HashMap<>();            Map<RandomListNode,Integer>  remap = new HashMap<>();            Map<Integer, RandomListNode> newMap = new HashMap<>();            RandomListNode newHead = new RandomListNode(-1);            RandomListNode iter = head , newIter = newHead;            int count = 0;            while(iter!=null)            {                newIter.next = new RandomListNode(iter.label);                map.put(count, iter.random);                remap.put(iter, count);                newMap.put(count,newIter.next);                newIter = newIter.next;                iter =iter.next;                count++;            }            newIter = newHead.next;            count = 0;            while(newIter!=null)            {                RandomListNode ran = map.get(count);                if(ran==null)                    newIter.random = null;                else                {                    int key = remap.get(ran);                    newIter.random = newMap.get(key);                }                newIter = newIter.next;                count++;            }            return newHead.next;     }}