Increasing Order Search Tree

Leetcode - Increasing Order Search Tree

Submission

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
class Solution {
    public TreeNode increasingBST(TreeNode root) {
        if (root == null) return null;

        if (root.left == null) {
            root.right = increasingBST(root.right);
            return root;
        } else {
            TreeNode node = increasingBST(root.left);
            root.right = increasingBST(root.right);
            root.left = null;
            TreeNode current = node;
            while(current.right != null) {
                current = current.right;
            }
            current.right = root;
            return node;
        }
    }
}

Better Submission

public TreeNode increasingBST(TreeNode root, TreeNode tail) {  
    if (root == null) return tail;  

    TreeNode res = increasingBST(root.left, root);  
    root.left = null;  
    root.right = increasingBST(root.right, tail);  
    return res;  
}