Copy List with Random Pointer

最新推荐文章于 2025-05-21 11:23:47 发布

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本文介绍了一种复制带随机指针的单链表的方法，通过使用哈希映射，实现链表节点及其随机指向节点的高效复制。

/**
 * 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) {
        // Note: The Solution object is instantiated only once and is reused by each test case.
        if (!head) return NULL;
        unordered_map<RandomListNode *, RandomListNode *> map;  
        RandomListNode *res= new RandomListNode(head->label);
        RandomListNode *pre=res;
        map[head]=res;
        RandomListNode *temp=head->next;
        while(temp!=NULL) {
            RandomListNode *cur = new RandomListNode(temp->label);
            map[temp]=cur;
            pre->next=cur;
            pre=cur;
            temp=temp->next;
        }
        temp=head;
        RandomListNode *cur=res;
        while(temp!=NULL) {
            RandomListNode *x=map[temp];
            RandomListNode *y=map[temp->random];
            x->random=y;
            temp=temp->next;
        }
        return res;
    }
};

If we can modify the original list, there could be another way with the same idea but no need to use a map

/**
 * 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) {
        // Note: The Solution object is instantiated only once and is reused by each test case.
        if (!head) return NULL;
        RandomListNode *res= new RandomListNode(head->label);
        RandomListNode *pre=res;
        RandomListNode *temp=head->next;
        while(temp!=NULL) {
            RandomListNode *cur = new RandomListNode(temp->label);
            pre->next=cur;
            pre=cur;
            temp=temp->next;
        }
        temp=head;
        RandomListNode *cur=res;
        while(temp!=NULL) {
            pre=temp;
            temp=temp->next;
            pre->next = cur;
            cur=cur->next;
        }
        temp=head;
        cur=res;
        while(cur!=NULL) {
            temp ->next ->random = temp->random;
            temp=temp->next;
            cur=cur->next;
        }
        return res;
    }
};