Leetcode-problems/problem199.java at main · tejatayi/Leetcode-problems · GitHub

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//199. Binary Tree Right Side View

import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;
import java.util.Queue;


class TreeNode {
    int val;
    TreeNode left;
    TreeNode right;

    TreeNode() {}

    TreeNode(int val) {
        this.val = val;
    }

    TreeNode(int val, TreeNode left, TreeNode right) {
        this.val = val;
        this.left = left;
        this.right = right;
    }
}

public class problem199 {


    public static List<Integer> rightSideView(TreeNode root) {

        List<Integer> ans = new ArrayList<>();

        if(root==null)
        return ans;

        Queue <TreeNode> q = new LinkedList<>();
        q.add(root);

        while(!q.isEmpty())
        {
            int sz = q.size();
            for(int i=1;i<=sz;i++)
            {
                TreeNode curr = q.poll();

                if(curr.left!=null)
                q.add(curr.left);
                if(curr.right!=null)
                q.add(curr.right);

                if(i==sz)
                ans.add(curr.val);
            }

        }
        return ans;

    }


     public static TreeNode buildTree(Integer[] arr) {
        if (arr.length == 0 || arr[0] == null) return null;

        TreeNode root = new TreeNode(arr[0]);
        Queue<TreeNode> queue = new LinkedList<>();
        queue.add(root);

        int i = 1;
        while (!queue.isEmpty() && i < arr.length) {
            TreeNode current = queue.poll();

            // Left child
            if (i < arr.length && arr[i] != null) {
                current.left = new TreeNode(arr[i]);
                queue.add(current.left);
            }
            i++;

            // Right child
            if (i < arr.length && arr[i] != null) {
                current.right = new TreeNode(arr[i]);
                queue.add(current.right);
            }
            i++;
        }

        return root;
    }


    public static void main(String[] args) {
        Integer[] treeArray = {1,2,3,4,null,null,null,5};

        // Construct the tree
        TreeNode root = buildTree(treeArray);


       System.out.println(rightSideView(root));

    }
}