Leetcode 116 Populating Next Right Pointers in Each Node

    struct TreeLinkNode {
      TreeLinkNode *left;
      TreeLinkNode *right;
      TreeLinkNode *next;
    }

         1
       /  \
      2    3
     / \  / \
    4  5  6  7

         1 -> NULL
       /  \
      2 -> 3 -> NULL
     / \  / \
    4->5->6->7 -> NULL

/**
 * 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 ;
        if(root->left) 
        {
            root->left->next=root->right;
            connect(root->left);
        }
        if(root->right) 
        {
            if(root->next) root->right->next=root->next->left;
            connect(root->right);
        }
    }
};