Leetcode-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 shoshould look like:

   1         2             3                 4                     5                         6

Click to show hints.

Hints:

If you notice carefully in the flattened tree, each node's right child points to the next node of a pre-order traversal.

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

Leetcode-flatten binary tree to linked list