LeetCode/117.cpp at master · guihunkun/LeetCode · GitHub

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/*
// 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;
        queue<Node*> q{{root}};
        while(!q.empty())
        {
            int n=q.size();
            for(int i=0;i<n;i++)
            {
                Node* t=q.front();
                q.pop();
                if(i != n-1) {
                    Node* tNext=q.front();
                    t->next=tNext;
                }
                if(t->left)
                    q.push(t->left);
                if(t->right)
                    q.push(t->right);
            }
        }
        return root;
    }
};