Given a binary tree where all the right nodes are either leaf nodes with a sibling (a left node that shares the same parent node) or empty, flip it upside down and turn it into a tree where the original right nodes turned into left leaf nodes. Return the new root.
Example
Example1
Input: {1,2,3,4,5}
Output: {4,5,2,#,#,3,1}
Explanation:
The input is
1
/ \
2 3
/ \
4 5
and the output is
4
/ \
5 2
/ \
3 1
Example2
Input: {1,2,3,4}
Output: {4,#,2,3,1}
Explanation:
The input is
1
/ \
2 3
/
4
and the output is
4
\
2
/ \
3 1
public class Solution {
public TreeNode upsideDownBinaryTree(TreeNode root) {
if (root == null)
return null;
if (root.left == null && root.right == null)
return root;
// At this point it is stated, that left is guaranteed to exist
TreeNode ans = upsideDownBinaryTree(root.left);
root.left.right = root;
root.left.left = root.right;
root.left = null;
root.right = null;
return ans;
}
}