LeetCode - Populating Next Right Pointers in Each Node

 1 /**
 2  * Definition for binary tree with next pointer.
 3  * struct TreeLinkNode {
 4  *  int val;
 5  *  TreeLinkNode *left, *right, *next;
 6  *  TreeLinkNode(int x) : val(x), left(NULL), right(NULL), next(NULL) {}
 7  * };
 8  */
 9 class Solution {
10 public:
11     void connect(TreeLinkNode *root) {
12         if (root == NULL)
13         {
14             return;
15         }
16         
17         //任一节点的左儿子的next连右儿子
18         if (root->left != NULL)
19         {
20             root->left->next = root->right;
21         }
22         
23         //处理5连6情况
24         //若2的next不为NULL，5连2的next的left
25         if (root->right != NULL)
26         {
27             root->right->next = (root->next == NULL ? NULL : root->next->left);
28         }
29         
30         //递归每个节点
31         connect(root->left);
32         connect(root->right);
33     }
34 };