leetcode Copy List with Random Pointer

最新推荐文章于 2019-10-21 22:50:54 发布

原创最新推荐文章于 2019-10-21 22:50:54 发布 · 930 阅读

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本文介绍了一种复杂链表结构的深拷贝方法，该链表每个节点包含一个额外的随机指针。文章详细展示了如何通过一次遍历实现节点复制，并通过第二次遍历来设置随机指针，最后拆分原始链表和拷贝链表。

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.

Take advantage of the original list, but there is a WA code. Don't break the structure after allocate the random pointers.

/**
 * 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) {
    if (!head)
      return NULL;
    RandomListNode *cur = head, *curcopy = NULL, *next = NULL, *res =NULL, *dummy = new RandomListNode(-1), *l2 = dummy; 
    while (cur != NULL) {
      next = cur->next;
      cur->next = new RandomListNode(cur->label);
      cur->next->next = next;
      cur = next;
    }
    cur = head;
    while (cur != NULL) {
      next = cur->next->next;
      l2->next = cur->next;
      l2 = l2->next;
      if (cur->random)
        l2->random = cur->random->next;
      cur->next = next;
      cur = next;
    }
    res = dummy->next;
    delete dummy;
    return res;
  }
};

The right code is :

/**
 * 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) {
    if (!head)
      return NULL;
    RandomListNode *cur = head, *curcopy = NULL, *next = NULL, *res =NULL, *dummy = new RandomListNode(-1), *l2 = dummy; 
    while (cur != NULL) {
      next = cur->next;
      cur->next = new RandomListNode(cur->label);
      cur->next->next = next;
      cur = next;
    }
    cur = head;
    while (cur != NULL) {
      if (cur->random)
        cur->next->random = cur->random->next;
      cur = cur->next->next;
    }
    cur = head;
    while (cur != NULL) {
      next = cur->next->next;
      l2->next = cur->next;
      l2 = l2->next;
      cur->next = next;
      cur = next;
    }
    res = dummy->next;
    delete dummy;
    return res;
  }
};