levelTraversal.cpp

// Recursive C program for level order traversal of Binary Tree
#include <stdio.h>
#include <stdlib.h>
#include<queue>
using namespace std;
/* A binary tree node has data, pointer to left child
   and a pointer to right child */
struct node
{
    int data;
    struct node* left, *right;
};
 
/* Function protoypes */
void printGivenLevel(struct node* root, int level);
int height(struct node* node);
struct node* newNode(int data);
 
/* Function to print level order traversal a tree*/
void printLevelOrder(struct node* root)
{
    struct node *temp = root;
    queue<struct node *> q;
    q.push(temp);
        while(!q.empty())
        {
            temp = q.front();
            printf("%d\n",temp->data);
            if(temp->left != NULL)
                q.push(temp->left);
            if(temp->right != NULL)
                q.push(temp->right);
            q.pop();
        }
}
/* Helper function that allocates a new node with the
   given data and NULL left and right pointers. */
struct node* newNode(int data)
{
    struct node* node = (struct node*)
                        malloc(sizeof(struct node));
    node->data = data;
    node->left = NULL;
    node->right = NULL;
 
    return(node);
}
 
/* Driver program to test above functions*/
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);
 
    printf("Level Order traversal of binary tree is \n");
    printLevelOrder(root);
 
    return 0;
}