leetcode copy list with random pointer

来源：互联网发布：外汇数据接口api 编辑：程序博客网时间：2024/06/05 05:08

不太熟练，拖了几天终于AC了。不过空间复杂度略高。。

struct RandomListNode {     int label;     RandomListNode *next, *random;     RandomListNode(int x) : label(x), next(NULL), random(NULL) {} };RandomListNode *copyRandomList(RandomListNode *head) {RandomListNode *cp = NULL;vector<int> labs;vector<RandomListNode *> randList;if(!head)return cp;labs.push_back(head->label);head->label = 0;cp = new RandomListNode(0);int i = 0;RandomListNode *pcp=cp, *phead=head;//tag nodeswhile(phead->next){i++;RandomListNode *newcp = new RandomListNode(i);labs.push_back(phead->next->label);pcp->next = newcp;phead->next->label= i;phead = phead->next;randList.push_back(pcp);pcp = newcp;}randList.push_back(pcp);//set random pointspcp = cp;phead = head;RandomListNode *tmp = cp;i = 0;while(phead){if(phead->random){pcp->random = randList[phead->random->label];}phead = phead->next;pcp = pcp->next;i++;}//reset labels  i = 0;pcp = cp;phead = head;while(phead){phead->label = labs[i];pcp->label = labs[i];phead = phead->next;pcp = pcp->next;i++;}return cp;}

leetcode上也有一些非常取巧的办法，比如利用指针地址都是连续的，然后取新链表和原链表的地址差，从而可以快速深拷贝，空间复杂度还很低：

RandomListNode *copyRandomList(RandomListNode *head) {    if(head == NULL) return NULL;    RandomListNode *newHead = new RandomListNode(head->label);    newHead->random = head->random;    head->label = newHead - head;    RandomListNode *p = head->next, *q = newHead, *t;    while(p) {        t = new RandomListNode(p->label);        t->random = p->random;        p->label = t - p;        q->next = t;        q = t;        p = p->next;    }    q = newHead;    while(q) {        if(q->random)            q->random = q->random + q->random->label;        q = q->next;    }    p = head;    q = newHead;    while(p) {        p->label = q->label;        p = p->next;        q = q->next;    }    return newHead;}

当然最厉害的还是重合的思想，都是奇思妙想啊：

RandomListNode *copyRandomList(RandomListNode *head) {    if(head == NULL) return NULL;    RandomListNode *p = head;    do {        RandomListNode *q = p->next;        p->next = new RandomListNode(p->label);        p->next->next = q;        p = q;    } while(p != NULL);    p = head;    do {        p->next->random = (p->random == NULL) ? NULL : p->random->next;        p = p->next->next;    } while(p != NULL);    p = head;    RandomListNode *r = head->next;    for(RandomListNode *q = r;;) {        p->next = q->next;        p = p->next;        if(p == NULL) break;        q->next = p->next;        q = q->next;    }    return r;}

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