Difference between nodes of alternate vertical levels in a tree

The question below is given in the format in which questions are asked on Online Competitive coding Platforms.

You can see the question live on hackerrank.com at the link below: https://www.hackerrank.com/contests/rtech-april-18-01/challenges/vertical-level-sum-differences

Some of the solutions are:

Java

import java.io.*;
import java.util.*;
public class Solution {
    Node root;
    static int odd=0,even=0;
    public static class Node{
        int data;
        Node left;
        Node right;
        Node(int data){
            this.data=data;
            left=null;
            right=null;
        }
    }
    public static Node insert(int a[],Node root,int i){
        if (i < a.length) {
            if(a[i]==-1){
             Node temp = null;
            }
            else{
                Node temp = new Node(a[i]);
                root = temp;
             root.left = insert(a, root.left,2 * i + 1);
            root.right = insert(a, root.right, 2 * i + 2);
            }
        }
        return root;
    }
    public static void print(Node root,int i){
        if(root!=null){
            print(root.left,i-1);
            if(i%2==0)
                even+=root.data;
            else
                odd+=root.data;
            //System.out.println(root.data);
            print(root.right,i+1);
        }
    }
    public static void main(String[] args) {
        /* Enter your code here. Read input from STDIN. Print output to STDOUT. Your class should be named Solution. */
        Scanner sc=new Scanner(System.in);
        int n=sc.nextInt();
        int a[]=new int[n];
        for(int i=0;i<n;i++)
            a[i]=sc.nextInt();
        Solution sol=new Solution();
        sol.root=insert(a,sol.root,0);
        print(sol.root,0);
        System.out.println((even)-(odd));
    }
}

C++ Solution:

int a[100005];
int b[100005];
int main()
{
    int n;
    cin >> n;
    for(int i = 1 ; i<=n ; i++) { cin >> a[i];
    }
    b[1] = 0;
    for(int i = 1 ; i<=n ; i++)
    {
        b[2*i] = b[i]-1;
        b[2*i+1] = b[i]+1;
    }
    int even = 0 , odd = 0;
    for(int i = 1 ; i<=n ; i++)
    {
        if(abs(b[i])%2==0)
        {
            if(a[i]!=-1)
            {
                even+=a[i];
            }
        }
        else
        {
            if(a[i]!=-1)
            {
                odd+=a[i];
            }
        }
    }
    cout << even - odd;
    return 0;
}