Binary Tree : Odd-Even level Sum

/*

    Author :    Asim Krishna Prasad

    Program to get the sum of the nodes on the even level and odd level
    in a binary tree

    Note : Taking the level of root as 0
            Uncomment the commented codes to understand the execution better

*/

#include<stdio.h>
#include<stdlib.h>

#define scan(a)     scanf("%d", &a)
#define print(a)    printf("%d", a)
#define nline       printf("\n")
#define fl(i,a,b)   for(i=a; i<b; i++)

struct node
{
    int data;
    struct node* right, *left;
};

struct node* root=NULL;
struct node* end=NULL;

int arr[2];

struct node* insert(int ndata, struct node* curr)
{

    if(curr==NULL)
    {
        //printf("inserting here"); nline;
        struct node* temp;
        temp=(struct node*)(malloc(sizeof(struct node)));
        temp->data=ndata;
        temp->left=temp->right=NULL;
        curr=temp;
        //printf("returning from insertion now"); nline;
        return curr;
    }
    if(curr->data>ndata)
    {
        //printf("going to the left child"); nline;
        curr->left=insert(ndata,curr->left);
        //printf("coming back after inserting to the left child"); nline;
    }

    else
    {
        //printf("going to the right child"); nline;
        curr->right=insert(ndata,curr->right);
        //printf("coming back after inserting to the right child"); nline;
    }
    return curr;
}

void traverse(struct node* curr, int level)
{
    if(curr==NULL)
        return;
    traverse(curr->left, level+1);
    //print(curr->data); printf(" "); print(level); nline;
    arr[level%2]+=curr->data;
    traverse(curr->right, level+1);
}

int main()
{
    int n, m, i, j, k;
    printf("Enter the number of nodes to be inserted : ");
    scan(n);
    printf("Enter the elements one-by-one : \n");
    fl(i,0,n)
    {
        scan(k);
        root=insert(k,root);
    }
    traverse(root, 0);
    printf("Sum of the nodes on the even levels : "); print(arr[0]); nline;
    printf("Sum of the nodes on the odd levels : "); print(arr[1]); nline;
    return 0;
}