Binary Tree implementation in C

BinaryTree.c

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

// Initialization ----------------------------------------------------------------------------------
struct  node {
  int data;
  struct node* left;
  struct node* right;
};

struct node* root = NULL;

//prototyping----------------------------------------------------------------------------------------
struct node * insert(struct node *, int);
struct node * getnew (int);
void search (struct node * , int);
int preorder(struct node* );
int postorder(struct node* );
int inorder(struct node* );
struct node * delete(struct node*, int);

//---------------------------------------------------------------------------------------------------
int main(){
  
  while(1){
    printf("\nChoose\n");
    printf(" 1. Insert \n 2. Search \n 3. Preorder Traversal \n 4. Postorder Traversal \n 5. Inorder Traversal \n 6. Delete element \n 0. exit \n");
    printf("\nEnter your choice : ");
    int option;
    scanf("%d",&option);

    switch (option)
    {
      case 1 : {printf("\nEnter the data of node : ");
                int data;
                scanf("%d", &data);
                root = insert(root,data);      
                break;}
      case 2 : {if(root == NULL){
                  printf("\nTree is empty\n");}
                else{
                  printf("\nEnter the data you want to search : ");
                  int data1;
                  scanf("%d",&data1);
                  search(root,data1);}
                break;}
      case 3 : {if(root == NULL){
                  printf("\nTree is empty\n");}
                else{
                  preorder(root);}
                break;}
      
      case 4 : {if(root == NULL){
                  printf("\nTree is empty\n");}
                else{
                  postorder(root);}
                break;}

      case 5 : {if(root == NULL){
                  printf("\nTree is empty\n");}
                else{
                  inorder(root);}
                break;}

      case 6 : {if(root == NULL){
                  printf("\nTree is empty\n");}
                else{
                  printf("\nEnter the element you want to delete : ");
                  int data2;
                  scanf("%d",&data2);
                  if (root -> data == data2){
                    printf("\nYou can not delete root element\n");
                  }
                  else{
                    delete(root,data2);}
                }
                break;}

      case 0 :  exit(0);
                break;
    
      default:
                break;
    }
  }
  return 0;
}
//---------------------------------------------------------------------------------------------------
struct node* getnew(int data){
  struct node* temp;
  temp = (struct node*)malloc(sizeof(struct node));
  temp -> right = NULL;
  temp -> data = data;
  temp -> left = NULL;
  return temp;
}
//---------------------------------------------------------------------------------------------------
struct node* insert(struct node * root, int data){  

  if(root == NULL){    
    root = getnew(data);    
  }

  else if( data <= root -> data){
    root -> left = insert(root -> left, data);
  }

  else {
    root -> right = insert(root -> right ,data);
  }
  return root;

}
//---------------------------------------------------------------------------------------------------
void search(struct node * root , int data){

  if (root == NULL) printf("\nNo\n");
  else if (root ->data == data) printf("\nYes\n");
  else if (data <= root -> data) return search(root -> left, data);
  else return search (root -> right , data);
}
//---------------------------------------------------------------------------------------------------
int preorder(struct node* root){
  
  if(root == NULL){
    return 1;
    
  }
  
  else {
    
    printf("%d  ", root -> data);
    if (root-> left){
      preorder(root -> left);
    }
    if (root -> right){
      preorder(root -> right);
    }
    
  }
  return 1;
}
//---------------------------------------------------------------------------------------------------
int postorder(struct node* root){

  if(root == NULL){
    return 1;
    
  }
  
  else {
    if (root-> left){ 
      postorder(root -> left);
    }
    if (root -> right){
      postorder(root -> right);
    }
    printf("%d  ", root -> data);
    
  }
  return 1;

}
//---------------------------------------------------------------------------------------------------
int inorder(struct node* root){

  if(root == NULL){
    return 1;
    
  }
  
  else {
      
    if (root-> left){
      inorder(root -> left);
    }
    printf("%d  ", root -> data);
    if (root -> right){
      inorder(root -> right);
    }
    
  }
  return 1;

}
//---------------------------------------------------------------------------------------------------
struct node* delete (struct node* root,int data){
  if (root == NULL) return NULL;
  else if (root ->data == data){
    if (root -> left){
      return root ->left;
    }
    else if (root -> right){
      return root -> right;
    }
    free(root);
    
  }
  else if (data <= root -> data){
    struct node * ret, *temp;
    ret = delete(root -> left, data);
    if (ret != NULL ){
      temp = root -> left;
      free(temp);
      root -> left = ret;
    }
  } 
  else {
    struct node * ret, *temp;
    ret = delete(root -> right, data);
    if (ret != NULL ){
      temp = root -> right;
      free(temp);
      root -> right = ret;
    }
  } 
  return 0;
}