/**
 * 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) return;
        queue<TreeLinkNode*> t;
        t.push(root);
        while(!t.empty()){
            int s = t.size();
            TreeLinkNode* last = t.front(); t.pop();
            if(last->left) t.push(last->left);
            if(last->right) t.push(last->right);
            for(int i=1;i<s;i++){
                TreeLinkNode* tt = t.front(); t.pop();
                if(tt->left) t.push(tt->left);
                if(tt->right) t.push(tt->right);
                last->next = tt;
                last = tt;
            }
            last->next = NULL;
        }
    }
};