postOrder traversal in binary tree

#include <stdio.h>
#include <malloc.h>

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

 struct node *createNode(int data){
     struct node*n;
     n=(struct node *)malloc(sizeof(struct node));
     n->data=data;
     n->left=NULL;
     n->right=NULL;
     return n;
 }

void postOrder(struct node *root){
    if(root!=NULL){
        postOrder(root->left);
        postOrder(root->right);
        printf("%d ",root->data);
    }
}

int main(){
    struct node *p = createNode(4);
    struct node *p1 = createNode(1);
    struct node *p2 = createNode(6);
    struct node *p3 = createNode(5);
    struct node *p4 = createNode(2);
    
    p->left = p1;
    p->right = p2;
    p1->left = p3;
    p1->right = p4;
    
    postOrder(p);
    
    return 0;
}