leetcode: Copy List with Random Pointer

最新推荐文章于 2017-12-09 20:10:05 发布

martin_liang

最新推荐文章于 2017-12-09 20:10:05 发布

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分类专栏：算法 C++/C leetcode

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本文介绍了一种复杂链表结构的深拷贝方法，这种链表除了常规的next指针外还包含了一个指向链表中任意节点或null的随机指针。通过巧妙地插入新节点并调整指针连接，实现对原始链表的有效复制。

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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.

/**
 * 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) {
        
        RandomListNode *pCurNode = head;
        RandomListNode *pNewHead = NULL;
        RandomListNode *pNewNode = NULL;
        
        if (!head)
            return NULL;
        
        while (pCurNode)
        {
            RandomListNode *tmpNode = new RandomListNode(pCurNode->label);
            tmpNode->next = pCurNode->next;
            pCurNode->next = tmpNode;
            
            /* 
            * wrong here, because the pCurNode->random may point to other node, 
            * so pCurNode->random->next may not point to the correct newCopy node
            */
            
            /*
            if (pCurNode->random)
            {
                tmpNode->random = pCurNode->random->next;
            }
            */
            pCurNode = pCurNode->next->next;
        }
        
        pCurNode = head;
        while (pCurNode)
        {
            if (pCurNode->random)
            {
                pCurNode->next->random = pCurNode->random->next;
            }
            pCurNode = pCurNode->next->next;
        }
        
        pCurNode = head;
        pNewHead = head->next;
        pNewNode = pNewHead;
        while (pCurNode)
        {
            pCurNode->next = pCurNode->next->next;
            
            if (pNewNode->next)
            {
                pNewNode->next = pNewNode->next->next;
            }
            
            pCurNode = pCurNode->next;
            pNewNode = pNewNode->next;
        }

        return pNewHead;
    }
};