Flatten Binary Tree to Linked List

Flatten Binary Tree to Linked List

Given a binary tree, flatten it to a linked list in-place.

For example,
Given

         1
        / 
       2   5
      /    
     3   4   6

The； flattened tree should look like:

   1
    
     2
      
       3
        
         4
          
           5
            
             6

分析： 这道题目的求解思路是对于某个既含有左子树又含有右子树的节点T，寻找左子树的中最靠右的叶子节点，将T的右子树挂在该叶子节点的右节点上，再将T的左边节点移动到右边，依次遍历右子树

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    void flatten(TreeNode* root) {
        while(root){
            if(root->left && root->right){
                TreeNode* t = root->left;
                while(t->right)
                    t = t->right;
                t->right=root->right;
            }
            if(root->left){
                root->right = root->left;
                root->left=NULL;
            }
                
            root = root->right;
            
        }   
        
        
    }
};