[Leetcode]扁平化多级双向链表

题目

 

https://leetcode-cn.com/explore/learn/card/linked-list/197/conclusion/764/

代码 

/*
// Definition for a Node.
class Node {
public:
    int val;
    Node* prev;
    Node* next;
    Node* child;

    Node() {}

    Node(int _val, Node* _prev, Node* _next, Node* _child) {
        val = _val;
        prev = _prev;
        next = _next;
        child = _child;
    }
};
*/
class Solution {
public:
    Node* flatten(Node* head) {
        if(head==nullptr)
            return nullptr;
        Node*ptr=head;
        
        while(ptr!=nullptr)
        {
            //当前结点有孩子结点
            if(ptr->child!=nullptr)
            {
                auto child=ptr->child;
                auto ptrNext=ptr->next;
                child->prev=ptr;
                ptr->next=child;
                ptr->child=nullptr;
                while(child->next!=nullptr)
                    child=child->next;
                //当前结点不是尾结点
                if(ptrNext!=nullptr)
                {
                    ptrNext->prev=child;
                    child->next=ptrNext;
                }
                
            }
                ptr=ptr->next;

        }
         return head;
    }
   
};