Pre to Post order Binary Search Tree

pre_to_post_binary_search_tree.c

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

typedef struct _btree {
  int n;
  struct _btree *left;
  struct _btree *right;
}BTree;

BTree * createNode() {
  BTree *node = (BTree*) malloc(sizeof(BTree));

  node->left = node->right = NULL;
  
  return node;
}

void read_preorder(int data,BTree **root) {


  if (*root == NULL) {
    *root = createNode();
    (*root)->n = data;
  } else
  
    if (data < (*root)->n) {
      if ((*root)->left !=NULL) {
	read_preorder(data,&((*root)->left));
      } else {
	(*root)->left = createNode();
	(*root)->left->n = data;
      }
    
    } else if (data > (*root)->n) {
      if ((*root)->right != NULL) {
	read_preorder(data,&((*root)->right));
      } else {
	(*root)->right = createNode();
	(*root)->right->n = data;
      }
    }
}

void print_postorder(BTree *root) {
  if (root->left != NULL)
    print_postorder(root->left);
  
  if (root->right != NULL)
    print_postorder(root->right);
  
  printf("%d\n",root->n);
  
}

void delete_postorder(BTree *root) {
  if (root!= NULL) {
    if (root->left != NULL)
      delete_postorder(root->left);
  
    if (root->right != NULL)
      delete_postorder(root->right);
  
    free(root);
  }
  
}


int main() {
  BTree *root = NULL;
  int input;
  while(!feof(stdin)) {
    scanf("%d",&input);
    read_preorder(input,&root);
  }
  print_postorder(root);
  delete_postorder(root);
  return 0;
}