Skip to content
Related Articles

Related Articles

Improve Article

Print Binary Tree levels in sorted order | Set 2 (Using set)

  • Difficulty Level : Medium
  • Last Updated : 14 Jul, 2021

Given a tree, print the level order traversal in sorted order.
Examples : 
 

Input :     7
          /    \
        6       5
       / \     / \
      4  3    2   1
Output : 
7
5 6
1 2 3 4 

Input :     7
          /    \
        16       1
       / \      
      4   13    
Output :
7 
1 16
4 13

 

We have discussed a priority queue based solution in below post.
Print Binary Tree levels in sorted order | Set 1 (Using Priority Queue)
In this post, a set (which is implemented using balanced binary search tree) based solution is discussed.
Approach : 
1. Start level order traversal of tree. 
2. Store all the nodes in a set(or any other similar data structures). 
3. Print elements of set.
 

C++




// CPP code to print level order
// traversal in sorted order
#include <bits/stdc++.h>
using namespace std;
 
struct Node {
    int data;
    Node* left;
    Node* right;
    Node(int dat = 0)
        : data(dat), left(nullptr),
          right(nullptr)
    {
    }
};
 
// Function to print sorted
// level order traversal
void sorted_level_order(Node* root)
{
    queue<Node*> q;
    set<int> s;
 
    q.push(root);
    q.push(nullptr);
 
    while (q.empty() == false) {
        Node* tmp = q.front();
        q.pop();
 
        if (tmp == nullptr) {
            if (s.empty() == true)
                break;
            for (set<int>::iterator it =
                 s.begin();it != s.end(); ++it)
                cout << *it << " ";
            q.push(nullptr);
            s.clear();
        }
        else {
            s.insert(tmp->data);
 
            if (tmp->left != nullptr)
                q.push(tmp->left);
            if (tmp->right != nullptr)
                q.push(tmp->right);
        }
    }
}
 
// Driver code
int main()
{
    Node* root = new Node(7);
    root->left = new Node(6);
    root->right = new Node(5);
    root->left->left = new Node(4);
    root->left->right = new Node(3);
    root->right->left = new Node(2);
    root->right->right = new Node(1);   
    sorted_level_order(root);   
    return 0;   
}

Java




// Java code to print level order
// traversal in sorted order
import java.util.*;
import java.util.HashSet;
 
class GFG
{
static class Node
{
    int data;
    Node left, right;
};
static Node newNode(int data)
{
    Node node = new Node();
    node.data = data;
    node.left = node.right = null;
    return (node);
}
 
// Function to print sorted
// level order traversal
static void sorted_level_order(Node root)
{
    Queue<Node> q = new LinkedList<>();
    Set<Integer> s = new HashSet<Integer>();
    q.add(root);
    q.add(null);
 
    while (!q.isEmpty())
    {
        Node tmp = q.peek();
            q.remove();
 
        if (tmp == null)
        {
            if (s.isEmpty())
                break;
            Iterator value = s.iterator();
            while (value.hasNext())
            {
                System.out.print(value.next() + " ");
            }
            q.add(null);
            s.clear();
        }
        else
        {
            s.add(tmp.data);
 
            if (tmp.left != null)
                q.add(tmp.left);
            if (tmp.right != null)
                q.add(tmp.right);
        }
    }
}
 
// Driver Code
public static void main(String[] args)
{
    Node root = newNode(7);
    root.left = newNode(6);
    root.right = newNode(5);
    root.left.left = newNode(4);
    root.left.right = newNode(3);
    root.right.left = newNode(2);
    root.right.right = newNode(1);
    sorted_level_order(root);
}
}
 
// This code is contributed by SHUBHAMSINGH10

Python3




# Python3 program to print level order
# traversal in sorted order
 
# Helper function that allocates a new
# node with the given data and None
# left and right poers.                                    
class newNode:
 
    # Construct to create a new node
    def __init__(self, key):
        self.data = key
        self.left = None
        self.right = None
 
# Function to print sorted
# level order traversal
def sorted_level_order( root):
 
    q = []
    s = set()
 
    q.append(root)
    q.append(None)
 
    while (len(q)):
        tmp = q[0]
        q.pop(0)
 
        if (tmp == None):
            if (not len(s)):
                break
            for i in s:
                print(i, end = " ")
            q.append(None)
            s = set()
         
        else :
            s.add(tmp.data)
 
            if (tmp.left != None):
                q.append(tmp.left)
            if (tmp.right != None):
                q.append(tmp.right)
 
# Driver Code
if __name__ == '__main__':
     
    """
    Let us create Binary Tree shown
    in above example """
    root = newNode(7)
    root.left = newNode(6)
    root.right = newNode(5)
    root.left.left = newNode(4)
    root.left.right = newNode(3)
    root.right.left = newNode(2)
    root.right.right = newNode(1)
    sorted_level_order(root)
 
# This code is contributed by
# Shubham Singh(SHUBHAMSINGH10)

C#




// C# code to print level order
// traversal in sorted order
using System;
using System.Collections.Generic;
 
class GFG
{
public class Node
{
    public int data;
    public Node left, right;
};
 
static Node newNode(int data)
{
    Node node = new Node();
    node.data = data;
    node.left = node.right = null;
    return (node);
}
 
// Function to print sorted
// level order traversal
static void sorted_level_order(Node root)
{
    Queue<Node> q = new Queue<Node>();
    SortedSet<int> s = new SortedSet<int>();
    q.Enqueue(root);
    q.Enqueue(null);
 
    while (q.Count != 0)
    {
        Node tmp = q.Peek();
            q.Dequeue();
 
        if (tmp == null)
        {
            if (s.Count == 0)
                break;
            foreach (int v in s)
            {
                Console.Write(v + " ");
            }
            q.Enqueue(null);
            s.Clear();
        }
        else
        {
            s.Add(tmp.data);
 
            if (tmp.left != null)
                q.Enqueue(tmp.left);
            if (tmp.right != null)
                q.Enqueue(tmp.right);
        }
    }
}
 
// Driver Code
public static void Main(String[] args)
{
    Node root = newNode(7);
    root.left = newNode(6);
    root.right = newNode(5);
    root.left.left = newNode(4);
    root.left.right = newNode(3);
    root.right.left = newNode(2);
    root.right.right = newNode(1);
    sorted_level_order(root);
}
}
 
// This code is contributed by 29AjayKumar

Javascript




<script>
// Javascript code to print level order
// traversal in sorted order
var SortedSet = require("collections/sorted-set");
 
class Node
{
    constructor()
    {
        this.data=0;
        this.left=this.right=null;
    }
}
 
function newNode(data)
{
    let node = new Node();
    node.data = data;
    node.left = node.right = null;
    return (node);
}
 
// Function to print sorted
// level order traversal
function sorted_level_order(root)
{
    let q = [];
    let s = new SortedSet();
    q.push(root);
    q.push(null);
   
    while (q.length!=0)
    {
        let tmp = q.shift();
             
       
        if (tmp == null)
        {
            if (s.size==0)
                break;
            for(let i of s.values())
            {
                document.write(i+" ");
            }
            q.push(null);
            s.clear();
        }
        else
        {
            s.add(tmp.data);
   
            if (tmp.left != null)
                q.push(tmp.left);
            if (tmp.right != null)
                q.push(tmp.right);
        }
    }
}
 
// Driver Code
let root = newNode(7);
root.left = newNode(6);
root.right = newNode(5);
root.left.left = newNode(4);
root.left.right = newNode(3);
root.right.left = newNode(2);
root.right.right = newNode(1);
sorted_level_order(root);
 
 
// This code is contributed by rag2127
</script>
Output: 
7 5 6 1 2 3 4 

 

Attention reader! Don’t stop learning now. Get hold of all the important DSA concepts with the DSA Self Paced Course at a student-friendly price and become industry ready.  To complete your preparation from learning a language to DS Algo and many more,  please refer Complete Interview Preparation Course.

In case you wish to attend live classes with experts, please refer DSA Live Classes for Working Professionals and Competitive Programming Live for Students.




My Personal Notes arrow_drop_up
Recommended Articles
Page :