Populating Next Right Pointers in Each Node II问题及解法

问题描述：

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.

示例：
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

问题分析：

依次遍历每一层，根据parent节点寻找每个root节点的next值，迭代求解即可。

过程详见代码：

/** * 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) {TreeLinkNode  parent(0);parent.left = root;bl(root, &parent,1);}void bl(TreeLinkNode *root, TreeLinkNode * parent,int dirt){if (root == NULL) return;TreeLinkNode * tp = parent;TreeLinkNode * tr = root;        if (dirt == 1 && tp->right){tr->next = tp->right;tr = tr->next;}while (tp->next &&  tr->next == NULL){if (tp->next->left){tr->next = tp->next->left;tr = tr->next;}if (tp->next->right){tr->next = tp->next->right;tr = tr->next;}tp = tp->next;}bl(root->left, root,1);bl(root->right, root,2);}};