#填充每个节点指向最右节点的next指针 #基于queue

/**
 * Definition for binary tree with next pointer.
 * struct TreeLinkNode {
 *  int val;
 *  TreeLinkNode *left, *right, *next;
 *  TreeLinkNode(int x) : val(x), left(NULL), right(NULL), next(NULL) {}
 * };
 */
class Solution {
public:
    void connect(TreeLinkNode *root) {
        if(root==nullptr) return;
        deque<TreeLinkNode*> dq;
        dq.push_front(root);

        while(!dq.empty()){
            int n=dq.size();
            for(int i=0;i<n;i++){
                TreeLinkNode* node=dq.front();
                dq.pop_front();
                if(i<n-1){
                    node->next=dq.front();
                }
                else{
                    node->next=nullptr;
                }
                if(node->left) dq.push_back(node->left);
                if(node->right) dq.push_back(node->right);
            }
        }
    }
};