Binary Tree -Data Structure using C Language

#include<stdio.h>
#include<conio.h>
struct node
{
    int data;
    struct node *left;
    struct node *right;
};
struct node *root=NULL;
struct node *insert(struct node*,int);
void displayPreorder(struct node*);
void displayInorder(struct node*);
void displayPostorder(struct node*);
int count=1;
void main()
{
    int value,choice;
    while(1)
    {
        printf("\n1.Insert");
        printf("\n2.Display in pre order");
        printf("\n3.Display in In-order");
        printf("\n4.Display in Post order");
        printf("\n5.Exit");
        printf("\nEnter your choice\n");
        scanf("%d",&choice);
        switch(choice)
        {
        case 1:
            printf("Enter Value\n");
            scanf("%d",&value);
            root=insert(root, value);
            break;
        case 2:
            displayPreorder(root);
            break;
        case 3:
            displayInorder(root);
            break;
        case 4:
            displayPostorder(root);
            break;
        case 5:
            exit(1);
            break;
        default:
            printf("\nInvalid Input");
            break;


        }
    }
}

struct node *insert(struct node *r, int v)
{
    if(r==NULL)
    {
        r=(struct node*)malloc(sizeof(struct node));
        r->left=NULL;
        r->right=NULL;
        r->data=v;
        count++;
    }
    else{
        if(count%2==0)
        {
            r->left=insert(r->left,v);
        }
        else{
            r->right=insert(r->right,v);
        }
    }
    return r;
}
void displayPreorder(struct node *r)
{
    if(r!=NULL)
    {
        printf("%d\n",r->data);
        displayPreorder(r->left);
        displayPreorder(r->right);
    }
}

void displayInorder(struct node *r)
{
    if(r!=NULL)
    {
        displayInorder(r->left);
        printf("%d\n",r->data);
        displayInorder(r->right);
    }
}
void displayPostorder(struct node *r)
{
    if(r!=NULL)
    {
        displayPostorder(r->left);
        displayPostorder(r->right);
        printf("%d\n",r->data);
    }
}