[Linked List]Copy List with Random Pointer

Total Accepted: 53943 Total Submissions: 209664 Difficulty: Hard

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.

(M) Clone Graph

o(n)空间复杂度,代码比价简单。网上还流传一种o(1)空间复杂度的解法，大致的过程就是先拷贝next结点，再连接随机结点，最后分离链表。

/**
* 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) {
unordered_map<RandomListNode*,RandomListNode*> umap;
RandomListNode* newHead  = NULL;
RandomListNode* cur      = head;
RandomListNode* node_pre = NULL;
RandomListNode* node     = NULL;
while(cur){
node      = new RandomListNode(cur->label);
umap[cur] = node;
cur == head ? newHead = node :node_pre->next = node;
node_pre  = node;
cur       = cur->next;
}
cur = head;
while(cur){
umap[cur]->random = cur->random ? umap[cur->random] : NULL;
cur               = cur->next;
}
return newHead;
}
};

Next challenges: (M) Clone Graph