【LeetCode】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 connImpl(TreeLinkNode *n1, TreeLinkNode *n2)
    {
        if(!n1) return;
        n1->next=n2;
        connImpl(n1->left,n1->right);
        if(n2)
        {
            connImpl(n1->right,n2->left);
            connImpl(n2->left,n2->right);
            connImpl(n2->right,NULL);
        }
    }
    void connect(TreeLinkNode *root) {
        if(NULL==root) return;
        connImpl(root, NULL);
    }
}