Program to print nodes between two given level numbers of a binary tree using C++

In this tutorial, we will be discussing a program to print nodes between the two given level numbers of a binary tree.

In this, we will be given a low level and a high level for a particular binary tree and we have to print all the elements between the given levels.

To solve this we can use queue-based level traversal. While moving through inorder traversal we can have a marking node at the end of each level. Then we can go to each level and print its nodes if the marking node exists between the given levels.

Example

#include <iostream>
#include <queue>
using namespace std;
struct Node{
   int data;
   struct Node* left, *right;
};
//to print the nodes between the levels
void print_nodes(Node* root, int low, int high){
   queue <Node *> Q;
   //creating the marking node
   Node *marker = new Node;
   int level = 1;
   Q.push(root);
   Q.push(marker);
   while (Q.empty() == false){
      Node *n = Q.front();
      Q.pop();
      //checking for the end of level
      if (n == marker){
      cout << endl;
      level++;
      if (Q.empty() == true || level > high)
      break;
      Q.push(marker);
      continue;
   }
   if (level >= low)
      cout << n->data << " ";
      if (n->left != NULL) Q.push(n->left);
      if (n->right != NULL) Q.push(n->right);
   }
}
Node* create_node(int data){
   Node* temp = new Node;
   temp->data = data;
   temp->left = temp->right = NULL;
   return (temp);
}
int main(){
   struct Node *root= create_node(20);
   root->left= create_node(8);
   root->right= create_node(22);
   root->left->left= create_node(4);
   root->left->right= create_node(12);
   root->left->right->left= create_node(10);
   root->left->right->right= create_node(14);
   cout << "Elements between the given levels are :";
   print_nodes(root, 2, 3);
   return 0;
}

Output

Elements between the given levels are :
8 22
4 12