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Largest_BST.java
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Largest_BST.java
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// { Driver Code Starts
//Initial Template for Java
/*package whatever //do not write package name here */
import java.io.*;
import java.util.*;
import java.math.*;
class Node {
int data;
Node left, right;
public Node(int d) {
data = d;
left = right = null;
}
}
class GFG {
static Node buildTree(String str) {
// Corner Case
if (str.length() == 0 || str.equals('N'))
return null;
String[] s = str.split(" ");
Node root = new Node(Integer.parseInt(s[0]));
Queue<Node> q = new LinkedList<Node>();
q.add(root);
// Starting from the second element
int i = 1;
while (!q.isEmpty() && i < s.length) {
// Get and remove the front of the queue
Node currNode = q.remove();
// Get the curr node's value from the string
String currVal = s[i];
// If the left child is not null
if (!currVal.equals("N")) {
// Create the left child for the curr node
currNode.left = new Node(Integer.parseInt(currVal));
// Push it to the queue
q.add(currNode.left);
}
// For the right child
i++;
if (i >= s.length)
break;
currVal = s[i];
// If the right child is not null
if (!currVal.equals("N")) {
// Create the right child for the curr node
currNode.right = new Node(Integer.parseInt(currVal));
// Push it to the queue
q.add(currNode.right);
}
i++;
}
return root;
}
public static void main(String args[]) throws IOException {
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
int t = Integer.parseInt(br.readLine().trim());
while (t > 0) {
String s = br.readLine();
Node root = buildTree(s);
Solution T = new Solution();
System.out.println(T.largestBst(root));
t--;
}
}
}
class Solution {
static int largestBst(Node root) {
ArrayList<Integer> arr = new ArrayList<>();
arr = solve(root);
return arr.get(1);
}
static ArrayList<Integer> solve(Node root) {
ArrayList<Integer> ans = new ArrayList<>();
int max = Integer.MAX_VALUE;
int min = Integer.MIN_VALUE;
ArrayList<Integer> a1 = new ArrayList<>();
if (root == null) {
a1.add(1);
a1.add(0);
a1.add(max);
a1.add(min);
return a1;
}
if (root.left == null && root.right == null) {
a1.add(1);
a1.add(1);
a1.add(root.data);
a1.add(root.data);
return a1;
}
ArrayList<Integer> l = new ArrayList<>();
ArrayList<Integer> r = new ArrayList<>();
l = solve(root.left);
r = solve(root.right);
if (l.get(0) == 1 && r.get(0) == 1) {
if (root.data > l.get(3) && root.data < r.get(2)) {
int x = l.get(2);
int y = r.get(3);
if (x == max)
x = root.data;
if (y == min)
y = root.data;
ans.add(1);
ans.add(l.get(1) + r.get(1) + 1);
ans.add(x);
ans.add(y);
return ans;
}
}
ans.add(0);
ans.add(Math.max(l.get(1), r.get(1)));
ans.add(0);
ans.add(0);
return ans;
}
}