Find size of largest BST in bt trees challenges

#1

import java.util.*;
public class Main {

static Scanner scn = new Scanner(System.in);

public static void main(String[] args) {
	Main m = new Main();
	Scanner sc = new Scanner(System.in);
	int n = sc.nextInt();
	int[] pre = new int[n];
	for(int i=0;i<n;i++){
		pre[i] = sc.nextInt();
	}
	int[] in = new int[n];
	for(int i=0;i<n;i++){
		in[i] = sc.nextInt();
	}
	BinaryTree bt = m.new BinaryTree(pre, in);

// int largestBst = bt.largestBST();
}

private class BinaryTree {
	private class Node {
		
		int data;
		Node left;
		Node right;
		
		Node(int data){
			this.data = data;
		}
	}

	private Node root;
	private int size;

	public BinaryTree(int[] pre, int[] in) {
		this.root = this.construct(in,pre,0,in.length-1,0,pre.length-1);
	}

	private Node construct( int[] in,int[] pre,int inS,int inE,int preS,int preE) {
		if(inS>inE){
			return null;
		}

		int rootData = pre[preS];
		int rootIndex = -1;
		for(int i =inS;i<=inE;i++){
			if(in[i] == rootData){
				rootIndex = i;
				break;
			}
		}
		int lpreS = preS+1;
		int linS = inS; 
		int linE = rootIndex-1;
		int lpreE = linE - linS + lpreS;
		int rpreS = lpreS+1;
		int rpreE = preE;
		int rinS = rootIndex+1;
		int rinE = inE;

		Node nn = new Node(rootData);
		nn.left = construct(in,pre,linS,linE,lpreS,lpreE);
		nn.right = construct(in,pre,rinS,rinE,rpreS,rpreE);
		return nn;

		
	}
	
}}

//sir I’m using this code to create the tree but it is showing index out of bounds exception.
But, when I was using this for the problem construct tree from preorder and inorder traversal, it worked absolutely fine .

#2

@Siddharth_sharma1808
import java.util.*;

public class testing {

static Scanner scn = new Scanner(System.in);

public static void main(String[] args) {
	Scanner sc = new Scanner(System.in);
	int n = sc.nextInt();
	int[] pre = new int[n];
	for (int i = 0; i < n; i++) {
		pre[i] = sc.nextInt();
	}
	int[] in = new int[n];
	for (int i = 0; i < n; i++) {
		in[i] = sc.nextInt();
	}
	BinaryTree bt = new BinaryTree(pre, in);
	bt.display();

	// int largestBst = bt.largestBST();
}

private static  class BinaryTree {
	private class Node {

		int data;
		Node left;
		Node right;

		Node(int data) {
			this.data = data;
		}
	}

	private Node root;
	private int size;

	public BinaryTree(int[] pre, int[] in) {
		this.root = this.construct(in, pre, 0, in.length - 1, 0, pre.length - 1);
	}

	private Node construct(int[] in, int[] pre, int inS, int inE, int preS, int preE) {
		if (inS > inE) {
			return null;
		}

		int rootData = pre[preS];
		int rootIndex = -1;
		for (int i = inS; i <= inE; i++) {
			if (in[i] == rootData) {
				rootIndex = i;
				break;
			}
		}
		int lpreS = preS + 1;
		int linS = inS;
		int linE = rootIndex - 1;
		int lpreE = linE - linS + lpreS;
		int rpreS = lpreE + 1; //here you have written lpreS but it should be IpreE
		int rpreE = preE;
		int rinS = rootIndex + 1;
		int rinE = inE;

		Node nn = new Node(rootData);
		nn.left = construct(in, pre, linS, linE, lpreS, lpreE);
		nn.right = construct(in, pre, rinS, rinE, rpreS, rpreE);
		return nn;

	}

	public void display() {
        this.display(this.root);
    }

    private void display(Node node) {
        if (node.left != null) {
            System.out.print(node.left.data + " =>");
        } else {
            System.out.print("END =>");
        }
        System.out.print(node.data + "<= ");
        if (node.right != null) {
            System.out.print(node.right.data);
        } else {
            System.out.print("END");
        }
        System.out.println();
        if (node.left != null) {
            this.display(node.left);
        }
        if (node.right != null) {
            this.display(node.right);
        }
}

}
}

#3

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