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Top | MCQs on Queue Data Structure with Answers | Question 29

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What is wrong in the below code of printing Right View of a binary tree using the Queue data structure?

C++

#include <iostream>
#include <queue>
using namespace std;

class Node {
public:
    int data;
    Node* left;
    Node* right;
    Node(int val) : data(val), left(nullptr), right(nullptr) {}
};

void printRightView(Node* root) {
    if (root == nullptr) return;

    queue<Node*> q;
    q.push(root);
    while (!q.empty()) {
        int n = q.size();
        for (int i = 0; i < n; i++) {
            Node* x = q.front();
            q.pop();
            if (i == n - 1) {
                cout << x->data << " ";
            }
            if (x->left) {
                q.push(x->left);
            }
            if (x->right) {
                q.push(x->right);
            }
        }
    }
}

#include <stdio.h>
#include <stdlib.h>
struct Node {
    int data;
    struct Node* left;
    struct Node* right;
};

void printRightView(struct Node* root) {
    if (root == NULL) return;

    struct Node** queue = (struct Node**)malloc(100 * sizeof(struct Node*));
    int front = 0, rear = 0;
    queue[rear++] = root;
    while (front < rear) {
        int n = rear - front;
        for (int i = 0; i < n; i++) {
            struct Node* x = queue[front++];
            if (i == n - 1) {
                printf("%d ", x->data);
            }
            if (x->left) {
                queue[rear++] = x->left;
            }
            if (x->right) {
                queue[rear++] = x->right;
            }
        }
    }
    free(queue);
}

Java

import java.util.LinkedList;
import java.util.Queue;

class Node {
    int data;
    Node left, right;
    Node(int val) {
        data = val;
        left = right = null;
    }
}

public class Main {
    public static void printRightView(Node root) {
        if (root == null) return;

        Queue<Node> q = new LinkedList<>();
        q.add(root);
        while (!q.isEmpty()) {
            int n = q.size();
            for (int i = 0; i < n; i++) {
                Node x = q.poll();
                if (i == n - 1) {
                    System.out.print(x.data + " ");
                }
                if (x.left != null) {
                    q.add(x.left);
                }
                if (x.right != null) {
                    q.add(x.right);
                }
            }
        }
    }
}

Python

from collections import deque

class Node:
    def __init__(self, data):
        self.data = data
        self.left = None
        self.right = None

def printRightView(root):
    if root is None:
        return

    q = deque([root])
    while q:
        n = len(q)
        for i in range(n):
            x = q.popleft()
            if i == n - 1:
                print(x.data, end=' ')
            if x.left:
                q.append(x.left)
            if x.right:
                q.append(x.right)

JavaScript

class Node {
    constructor(data) {
        this.data = data;
        this.left = null;
        this.right = null;
    }
}

function printRightView(root) {
    if (root === null) return;

    let q = [root];
    while (q.length) {
        let n = q.length;
        for (let i = 0; i < n; i++) {
            let x = q.shift();
            if (i === n - 1) {
                process.stdout.write(x.data + ' ');
            }
            if (x.left) q.push(x.left);
            if (x.right) q.push(x.right);
        }
    }
}

We have not initialized anything in the Queue

Queue will never be empty.

left and right nodes of the tree are null.

None

This question is part of this quiz :

Top MCQs on Queue Data Structure with Answers

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