odd_levels_binary_tree.cpp

#include <bits/stdc++.h> 
using namespace std; 
  
struct Node { 
    int data; 
    Node* left, *right; 
}; 
  
void printOddNodes(Node *root, bool isOdd = true) 
{ 
    // If empty tree 
    if (root == NULL) 
      return; 
  
    // If current node is of odd level 
    if (isOdd) 
       cout << root->data << " " ; 
  
    // Recur for children with isOdd 
    // switched. 
    printOddNodes(root->left, !isOdd); 
    printOddNodes(root->right, !isOdd); 
} 
  
// Utility method to create a node 
struct Node* newNode(int data) 
{ 
    struct Node* node = new Node; 
    node->data = data; 
    node->left = node->right = NULL; 
    return (node); 
} 
  
// Driver code 
int main() 
{ 
    struct Node* root = newNode(1); 
    root->left = newNode(2); 
    root->right = newNode(3); 
    root->left->left = newNode(4); 
    root->left->right = newNode(5); 
    printOddNodes(root); 
  
    return 0; 
}