Binary Trees in C++ – 4 : Traversal

Question. Print the nodes of a binary tree along with their respective level numbers, in the order specified by preorder traversal.


We assume that the root is at level 0. The level number of any other node is 1 greater than the level number of its parent.

We can do the printing of the nodes and their level numbers quite easily using recursion.


struct Node


int data;

Node *left;

Node *right;


void pre_level (const Node *root, int level)


if ( ! root )


cout << root -> data << ”   LEVEL:   ” << level;

pre_level (root->left, level+1);

pre_level (root->right, level+1);



This code will run in O(n) time on a tree having n nodes.

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