#### Tree Random Node

A
```package com.thealgorithms.datastructures.trees;

/* Author : Suraj Kumar
Github : https://github.com/skmodi649
*/

/* PROBLEM DESCRIPTION :
There is a Binary Search Tree given, and we are supposed to find a random node in the given binary
tree.
*/

/* ALGORITHM :
Step 1: START
Step 2: First create a binary tree using the steps mentioned in the first approach
Step 3: Now use a method inOrder() that takes a node as input parameter to traverse through the
binary tree in inorder fashion as also store the values in a ArrayList simultaneously.
Step 4: Now define a method getRandom() that takes a node as input parameter, in this first call
the inOrder() method to store the values in the arraylist, then find the size of the
binary tree and now just generate a random number between 0 to n-1. Step 5: After generating the
number display the value of the ArrayList at the generated index Step 6: STOP
*/

import java.util.ArrayList;

// Using auxiliary array to find the random node in a given binary tree

public class TreeRandomNode {

private final class Node {

int item;
Node left;
Node right;
}

// Using an arraylist to store the inorder traversal of the given binary tree
static ArrayList<Integer> list = new ArrayList<>();
// root of Tree
Node root;

TreeRandomNode() {
root = null;
}

// Now lets find the inorder traversal of the given binary tree
static void inOrder(Node node) {
if (node == null) {
return;
}

// traverse the left child
inOrder(node.left);

// traverse the right child
inOrder(node.right);
}

public void getRandom(Node val) {
inOrder(val);
// getting the count of node of the binary tree
int n = list.size();
int min = 0;
int max = n - 1;
// Generate random int value from 0 to n-1
int b = (int) (Math.random() * (max - min + 1) + min);
// displaying the value at the generated index
int random = list.get(b);
System.out.println("Random Node : " + random);
}
}
/* Explanation of the Approach :
(a) Form the required binary tree
(b) Now use the inOrder() method to get the nodes in inOrder fashion and also store them in the
given arraylist 'list' (c) Using the getRandom() method generate a random number between 0 to n-1,
then get the value at the generated random number from the arraylist using get() method and
finally display the result.
*/
/* OUTPUT :
First output :
Random Node : 15
Second output :
Random Node : 99
*/
/* Time Complexity : O(n)
Auxiliary Space Complexity : O(1)
*/
```