Traversal binary tree

#include<stdio.h>
#include<stdlib.h>
struct node{
int data;
struct node *left;
struct node *right;
};
struct node *createnode(int data){
struct node *n = (struct node *)malloc(sizeof(struct node));
n -> data = data;
n -> left = NULL;
n -> right = NULL;
return n;
}
void preorder(struct node *root){
if(root != NULL){
printf("%d", root -> data);
preorder(root -> left);
preorder(root -> right);
}
}
void postorder(struct node *root){
if(root != NULL){
postorder(root -> left);
postorder(root -> right);
printf("%d",root -> data);
}
}
void inorder(struct node *root){
if(root != NULL){
inorder(root -> left);
printf("%d",root -> data);
inorder(root -> right);
}
}
int main()
{
struct node *p = createnode(7);
struct node *p1 = createnode(2);
struct node *p2 = createnode(1);
struct node *p3 = createnode(0);
struct node *p4 = createnode(4);
p -> left = p1;
p -> right = p2;
p1 -> left = p3;
p1 -> right = p4;
preorder(p);
printf("\n");
postorder(p);
printf("\n");
inorder(p);
return 0;

}