复杂链表的复制

struct RandomListNode {
    int label;
    struct RandomListNode *next, *random;
    RandomListNode(int x) :
            label(x), next(NULL), random(NULL) {
    }
};
class Solution {
public:
    RandomListNode* Clone(RandomListNode* pHead)
    {
        RandomListNode * newHead=NULL, *newPtr=NULL;
        RandomListNode *nowPtr=pHead;
        //不能赋值为0，否则特殊指针指向空指针时会出错
        int cnt = 1;
        map<RandomListNode*, int> node2index;
        node2index.clear();
        map<int, RandomListNode*> index2node;
        index2node.clear();
        while(nowPtr != NULL){
            if(newHead == NULL){
                newHead = new RandomListNode(nowPtr->label);
                newPtr = newHead;
                node2index[nowPtr] = cnt;
                index2node[cnt] = newHead;
                cnt++;
            }else{
                newPtr->next = new RandomListNode(nowPtr->label);
                newPtr = newPtr->next;
                node2index[nowPtr] = cnt;
                index2node[cnt] = newPtr;
                cnt++;
            }
            nowPtr = nowPtr->next;
        }
        newPtr=newHead;
        nowPtr = pHead;
        while(nowPtr != NULL){
            newPtr->random = index2node[node2index[nowPtr->random]];
            nowPtr = nowPtr->next;
            newPtr = newPtr->next;
        }
        return newHead;
    }
};