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/**
 * 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) {
    TreeLinkNode *now, *tail, *head;
    
    now = root;
    head = tail = NULL;
    while(now)
    {
        if (now->left)
            if (tail) tail = tail->next =now->left;
            else head = tail = now->left;
        if (now->right)
            if (tail) tail = tail->next =now->right;
            else head = tail = now->right;
        if(!(now = now->next))
        {
            now = head;
            head = tail=NULL;
        }
    }
}
};