Populating Next Right Pointers in Each Node II

Follow up for problem "Populating Next Right Pointers in Each Node".

What if the given tree could be any binary tree? Would your previous solution still work?

Note:

• You may only use constant extra space.

For example,
Given the following binary tree,

         1       /  \      2    3     / \    \    4   5    7

After calling your function, the tree should look like:

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

多了一个指针，记住root的位子，然后用一个helper指针来连接下层子树

/** * 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) {        while(root){            TreeLinkNode node(0);            TreeLinkNode* cur=&node;            while(root){                if (root->left){                    cur->next=root->left;                    cur=cur->next;                }                if (root->right){                    cur->next=root->right;                    cur=cur->next;                }                root=root->next;            }            root=node.next;        }    }};