Populating Next Right Pointers in Each Node

/**
 * 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 )
        {
            return ;
        }
        root->left->next = root->right;
        root->right->next = root->next ? root->next->left : NULL;
        connect( root->left );
        connect( root->right );
    }
};