## Algorithm

Problem Name: 897. Increasing Order Search Tree

Given the `root` of a binary search tree, rearrange the tree in in-order so that the leftmost node in the tree is now the root of the tree, and every node has no left child and only one right child.

Example 1:

```Input: root = [5,3,6,2,4,null,8,1,null,null,null,7,9]
Output: [1,null,2,null,3,null,4,null,5,null,6,null,7,null,8,null,9]
```

Example 2:

```Input: root = [5,1,7]
Output: [1,null,5,null,7]
```

Constraints:

• The number of nodes in the given tree will be in the range `[1, 100]`.
• `0 <= Node.val <= 1000`

## Code Examples

### #1 Code Example with Java Programming

```Code - Java Programming```

``````
class Solution {
public TreeNode increasingBST(TreeNode root) {
Stack stack = new Stack<>();
while (root != null) {
stack.push(root);
root = root.left;
}
while (!stack.isEmpty()) {
TreeNode removed = stack.pop();
}
TreeNode rightNode = removed.right;
while (rightNode != null) {
stack.push(rightNode);
rightNode = rightNode.left;
}
removed.right = stack.isEmpty() ? null : stack.peek();
removed.left = null;
}
}
}
``````
Copy The Code &

Input

cmd
root = [5,3,6,2,4,null,8,1,null,null,null,7,9]

Output

cmd
[1,null,2,null,3,null,4,null,5,null,6,null,7,null,8,null,9]

### #2 Code Example with Javascript Programming

```Code - Javascript Programming```

``````
const increasingBST = function(root) {
return helper(root, null)
};

function helper(node, tail) {
if(node == null) return tail
const res = helper(node.left, node)
node.left = null
node.right = helper(node.right, tail)
return res
}
``````
Copy The Code &

Input

cmd
root = [5,3,6,2,4,null,8,1,null,null,null,7,9]

Output

cmd
[1,null,2,null,3,null,4,null,5,null,6,null,7,null,8,null,9]

### #3 Code Example with Python Programming

```Code - Python Programming```

``````
class Solution:
def increasingBST(self, root, tail = None):
if not root: return tail
res = self.increasingBST(root.left, root)
root.left = None
root.right = self.increasingBST(root.right, tail)
return res
``````
Copy The Code &

Input

cmd
root = [5,1,7]

Output

cmd
[1,null,5,null,7]

### #4 Code Example with C# Programming

```Code - C# Programming```

``````
namespace LeetCode
{
public class _0897_IncreasingOrderSearchTree
{
private TreeNode currentRoot;

public TreeNode IncreasingBST(TreeNode root)
{
var dummy = new TreeNode(-1);
currentRoot = dummy;

InOrder(root);
return dummy.right;
}

private void InOrder(TreeNode node)
{
if (node == null) return;

InOrder(node.left);

node.left = null;
currentRoot.right = node;
currentRoot = node;

InOrder(node.right);
}
}
}
``````
Copy The Code &

Input

cmd
root = [5,1,7]

Output

cmd
[1,null,5,null,7]