Leetcode 114.二叉树展开为链表

二叉树展开为链表

给定一个二叉树，原地将它展开为链表。

例如，给定二叉树

将其展开为：

 class Solution{
 public:
     void flatten(TreeNode* root){
         if (root == NULL) return;
         flatten(root->left);
         flatten(root->right);
         TreeNode *temp = root->right;
         root->right = root->left;
         root->left = NULL;
         while (root->right) root = root->right;
         root->right = temp;
     }
 }