LeetCode 138——複制帶随機指針的連結清單

1. 題目

2. 解答

/**
 * 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 *> nodemap;
        RandomListNode *temp = head;
        RandomListNode *new_head = new RandomListNode(0); //哨兵節點，友善操作
        RandomListNode *copy_temp = new_head;
 
        // 建立新連結清單
        while (temp)
        {
            copy_temp->next = new RandomListNode(temp->label);
            nodemap[temp] = copy_temp->next;
            
            temp = temp->next;
            copy_temp = copy_temp->next;
        }
        
        RandomListNode *random_temp = NULL;
        temp = head;
        copy_temp = new_head->next;
        // 填充新連結清單的随機指針
        while (temp)
        {
            random_temp = temp->random;
            if (random_temp != NULL)   copy_temp->random = nodemap[random_temp];
            else    
                copy_temp->random = NULL;
            
            temp = temp->next;
            copy_temp = copy_temp->next;
        }
        
        return new_head->next;
    }
};