/**

 * 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 == NULL) return;

        if (root->left != NULL)

        {

            root->left->next = root->right;

            TreeLinkNode *go_deep_left = root->left->right;

            TreeLinkNode *go_deep_right = (root->right != NULL)?(root->right->left):NULL;

            while (go_deep_left != NULL && go_deep_right != NULL)

            {

                go_deep_left->next = go_deep_right;

                go_deep_left = go_deep_left->right;

                go_deep_right = go_deep_right->left;

            }

        }

        connect(root->right);

        connect(root->left);

    }

};