Given a binary tree, flatten it to a linked list in-place.
For example, given the following tree:
1
/
2 5
/ \
3 4 6
The flattened tree should look like:
1
2
3
4
5
6
class Solution {
private TreeNode prev = null;
public void flatten(TreeNode root) {
if(root == null) return ;
flatten(root.right);
flatten(root.left);
root.right = prev;
root.left = null;
prev = root;
}
}