[leetcode]Copy List with Random Pointer

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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.

劍指offer中的原題

演算法思路：

遍曆原list的每一個節點，對每一個節點產生一個copy節點，插到原節點的後面。完成next的拷貝

第二遍掃描，對每一個原節點的random節點，其copy節點的random應該為原節點random.next。完成random的拷貝

第三遍掃描，將copy list取下來。

【注意】：分解原list和copy list時候，要完整的把原list給組裝起來。不能破壞原list的結構。

 1 public class Solution { 2     public RandomListNode copyRandomList(RandomListNode head) { 3             if(head == null) return null; 4             RandomListNode node = head; 5             while(node != null){ 6                 RandomListNode tem = new RandomListNode(node.label); 7                 tem.next = node.next; 8                 node.next = tem; 9                 node = node.next.next;10             }11             node = head;12             while(node != null){13                 RandomListNode next = node.next;14                 if(node.random != null)15                     next.random = node.random.next;16                 node = node.next.next;17             }18             RandomListNode hhead = new RandomListNode(0);19             RandomListNode pointer = hhead;20             node = head;21             while(node != null){22                 pointer.next = node.next;23                 pointer = node.next;24                 node.next = node.next.next;25                 node = node.next;26             }27             return hhead.next;28         }29 }