LeetCode 117. 填充每个节点的下一个右侧节点指针 II

LeetCode 117. 填充每个节点的下一个右侧节点指针 II

思路：

用head与end去维护每一层的下一层，end维护next指针，head用来跳转到下一层。

代码：

/*
// Definition for a Node.
class Node {
public:
    int val;
    Node* left;
    Node* right;
    Node* next;

    Node() : val(0), left(NULL), right(NULL), next(NULL) {}

    Node(int _val) : val(_val), left(NULL), right(NULL), next(NULL) {}

    Node(int _val, Node* _left, Node* _right, Node* _next)
        : val(_val), left(_left), right(_right), next(_next) {}
};
*/

class Solution {
public:
    Node* connect(Node* root) {
        if(!root) return root;
        auto res = root;
        while(root){
            auto head =new Node(-1);
            auto end = head;
            for(auto p = root;p;p = p->next){
                if(p->left) end = end->next=p->left;
                if(p->right) end = end->next = p->right;
            }
            root = head->next;
        }
        return res;
    }
};