- Practice
- Functional Programming
- Memoization and DP
- Number of Binary Search Tree

# Number of Binary Search Tree

# Number of Binary Search Tree

A binary tree is a tree which is characterized by any of the following properties:

- It can be empty (null).
- It can contain a root node which contain some value and two subtree, left subtree and right subtree, which are also binary tree.

A binary tree is a binary search tree (BST) if all the non-empty nodes follows both two properties:

- If node has a left subtree, then all the values in its left subtree are smaller than the value of the current node.
- If node has a right subtree, then all the value in its right subtree are greater than the value of the current node.

You are given *N* nodes, each having unique value ranging from `[1, N]`

, how many different binary search tree can be created using all of them.

**Input**

First line will contain an integer, *T*, number of test cases. Then *T* lines follow, where each line represent a test case. Each test case consists a single integer, *N*, where *N* is the number of nodes in the binary search tree.

**Output**

For each test case, find the number of different binary search trees that can be created using these nodes. Print the answer modulo (10^{8}+7).

**Constraints**

1 <= *T* <= 1000

1 <= *N* <= 1000

**Sample Input**

```
5
1
2
3
4
100
```

**Sample Output**

```
1
2
5
14
25666077
```

**Explanation**

*Test Case #1:* We have only one tree.

```
1
```

*Test Case #2:* Two trees can be created using two nodes.

```
1 2
\ /
2 1
```

*Test Case #3:*

```
1 1 2 3 3
\ \ / \ / /
2 3 1 3 1 2
\ / \ /
3 2 2 1
```