Copy List with Random Pointer

Copy List with Random Pointer

问题：

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.

思路：

　　之前看过这道题，所以立马想到了对应的思路，node-->copynode-->node.next-->copynode.next

我的代码：

public class Solution {

    public RandomListNode copyRandomList(RandomListNode head) {

        if(head == null)    return head;

        RandomListNode cur = head;

        while(cur != null)

        {

            RandomListNode next = cur.next;

            RandomListNode tmp = new RandomListNode(cur.label);

            tmp.next = cur.next;

            cur.next = tmp;

            cur = next;

        }

        cur = head;

        while(cur != null)

        {

            RandomListNode next = cur.next.next;

            RandomListNode random = cur.random;

            if(random == null)  cur.next.random = null;

            else    cur.next.random = random.next;

            cur = next;

        }

        cur = head;

        RandomListNode rst = head.next;

        while(cur != null)

        {

            RandomListNode next = cur.next.next;

            if(next == null)

                cur.next.next = null;

            else

                cur.next.next = next.next;

            cur.next = next;

            cur = next;

        }

        return rst;

    }

}

View Code

他人代码：

public class Solution {

    public RandomListNode copyRandomList(RandomListNode head) {

        if (head == null) {

            return null;

        }



        HashMap<RandomListNode, RandomListNode> map = new HashMap<RandomListNode, RandomListNode>();

        RandomListNode dummy = new RandomListNode(0);

        RandomListNode pre = dummy, newNode;

        while (head != null) {

            if (map.containsKey(head)) {

                newNode = map.get(head);

            } else {

                newNode = new RandomListNode(head.label);

                map.put(head, newNode);

            }

            pre.next = newNode;



            if (head.random != null) {

                if (map.containsKey(head.random)) {

                    newNode.random = map.get(head.random);

                } else {

                    newNode.random = new RandomListNode(head.random.label);

                    map.put(head.random, newNode.random);

                }

            }



            pre = newNode;

            head = head.next;

        }



        return dummy.next;

    }

}

View Code

学习之处：

• Hashtable(node,copynode)方法也很不错嘛
• 自己的代码太长了，应该功能进行划分，划分成多个模块，一个这么长的代码不适合维护和阅读。