17.12. BiNode

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution:
    def convertBiNode(self, root: TreeNode) -> TreeNode:
        if root is None:
            return None
        left = self.convertBiNode(root.left)
        right = self.convertBiNode(root.right)
        if left is None:
            root.right = right
            return root
        res = left
        while left and left.right:
            left = left.right
        left.right = root
        root.right = right
        root.left = None
        return res

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    public TreeNode convertBiNode(TreeNode root) {
        if (root == null) return null;
        TreeNode left = convertBiNode(root.left);
        TreeNode right = convertBiNode(root.right);
        if (left == null) {
            root.right = right;
            return root;
        }
        TreeNode res = left;
        while (left != null && left.right != null) {
            left = left.right;
        }
        left.right = root;
        root.right = right;
        root.left = null;
        return res;
    }
}