Populating Next Right Pointers in Each Node II

Given a binary tree

Populate each next pointer to point to its next right node. If there is no next right node, the next pointer should be set to NULL.
Initially, all next pointers are set to NULL.

Example 1:

Input: root = {1,2,3,4,5,null,7}
Output: [1,#,2,3,#,4,5,7,#]

Approach

Java

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

public class PopulatingNextRightPointersII {
    public static void main(String[] args) {
        Node root = new Node(1);
        root.left = new Node(2);
        root.right = new Node(3);
        root.left.left = new Node(4);
        root.left.right = new Node(5);
        root.right.right = new Node(7);
        Node root1 = connect(root);
        printTree(root1);
    }

    // function to connect nodes at the
    // each level
    static Node connect(Node root) {
        Queue<Node> q = new LinkedList<>();
        if (root == null)
            return null;
        q.add(root);
        while (!q.isEmpty()) {
            int len = q.size();
            Node prev = null;
            while (len > 0) {
                len--;
                Node temp = q.poll();
                if (temp == null)
                    continue;
                if (prev != null)
                    prev.next = temp;
                else
                    prev = null;
                prev = temp;
                q.add(temp.left);
                q.add(temp.right);
            }
        }
        return root;
    }

//function to print the tree
    static void printTree(Node root) {
        Queue<Node> q = new LinkedList<>();
        q.add(root);
        List<String> vec = new ArrayList<String>();
        while (!q.isEmpty()) {
            int len = q.size();
            while (len > 0) {
                len--;
                root = q.poll();
                if (root != null) {
                    vec.add(String.valueOf(root.val));
                    q.add(root.left);
                    q.add(root.right);
                }
            }
            vec.add("#");
        }
        for (int i = 0; i < vec.size() - 2; i++)
            System.out.print(vec.get(i) + ",");
        System.out.println(vec.get(vec.size() - 2));
    }

    static class Node {
        int val;
        Node left;
        Node right;
        Node next;

        Node(int val) {
            this.val = val;
            this.next = null;
            this.right = null;
            this.left = null;
        }

    }
}

C++

#include <bits/stdc++.h>
using namespace std;

struct Node {
  int val;
  Node *left;
  Node *right;
  Node *next;
  Node(int val) 
     {
      this->val=val;
      this->next=NULL;
      this->right=NULL;
      this->left=NULL;
      }

};

//function to connect nodes at the 
//each level
Node* connect(Node* root) 
{
    queue<Node*> q;
    if(root==NULL)
       return NULL;
    q.push(root);
    while(!q.empty())
     {
         int len=q.size();
         Node *prev=NULL;
         while(len--)
         {
             Node *temp=q.front();
             q.pop();
             if(temp==NULL)
                    continue;
             prev?(prev->next=temp):NULL;
             prev=temp;
             q.push(temp->left);
             q.push(temp->right);
         }
     }
     return root;
}

//function to print the tree
void printTree(Node *root)
{
    queue<Node*>q;
    q.push(root);
    vector<string> vec;
    while(!q.empty())
     {
         int len=q.size();
         while(len--)
         {  
           root=q.front();
           q.pop();
        
           
        if(root!=NULL)
          {
               vec.push_back(to_string(root->val));
              q.push(root->left);
              q.push(root->right);
          }
         }
         vec.push_back("#");
     }
      for(int i=0;i<vec.size()-2;i++)
        cout<<vec[i]<<",";
     cout<<vec[vec.size()-2];
}
int main()
{
  Node *root=new Node(1);
  root->left=new Node(2);
  root->right=new Node(3);
  root->left->left=new Node(4);
  root->left->right=new Node(5);
  root->right->right=new Node(7);
  Node *root1=connect(root);
  printTree(root1);
  return 0;
}