Elements_btw_2_level_in_Binary_Tree_using_Queue.cpp

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

unordered_map <int, int> um;

struct Node
{
    int info;
    struct Node *left, *right;
};

struct Node* create()
{
    int data;
    Node *tree;
    tree = new Node;
    cout << "\nEnter data to be inserted or type -1 : ";
    cin >> data;

    if(data == -1)
        return 0;

    tree->info = data;

    cout << "Enter left child of " << data;
    tree->left = create();

    cout << "Enter right child of " << data;
    tree->right = create();

    return tree;
};

void printNodes(Node* root, int start, int end)
{
    if(root == NULL)
        return;

    queue <Node*> q;
    q.push(root);

    Node* curr = NULL;

    int level = 0;

    while(!q.empty() || curr)
    {
        level++;
        int size = q.size();

        while(size--)
        {
            curr = q.front();
            q.pop();

            if(level >= start && level <= end)
                cout<<curr->info<<" ";

            if(curr->left)
                q.push(curr->left);

            if(curr->right)
                q.push(curr->right);
        }
        if(level >= start && level <= end)
            cout<<endl;
    }
}

int main()
{
    Node *root = NULL;
    root = create();

    int level1 = 2;
    int level2 = 4;

    printNodes(root, level1, level2);

    return 0;
}