C program for Binary Search Tree with non duplicate values

Q. Write C language based code to create and operate on ADT : Binary Search Tree with unique positive integer values as Key Vaues:

(1). Create a BST with a single node as its Root Node;

(2). Add a node with a given Key Value (give error message, if Key Value already exists, else add a node); 

(3). Given a Key Value, delete a node if it exists; else give error message that the Key Value does not exist; 

(4). Perform search for a given Key Value; if it exists, output " Element Found", else output "Doesn't Exist in the tree";

(5). Perform In-order, Pre-order, Post-order traversal of a given BST and print Key Values in a row, separated by vertical bars; 

".C" file is available in downloadable format at :

https://drive.google.com/file/d/0ByF0OId1bLx6TFNUR0xnZE5za0U/view

(Open the link and click on the download arrow on the top right to download the file.)

Given below is the code for "C program for BST- Binary Search Tree with non duplicate values" :

-----------------------------------------------------------------------------------

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

typedef struct tree
{
int info;
struct tree* left;
struct tree* right;
}node;



node* create (node*); 
void insert (node*, node*);
node* search (node*, int);
node* del (node*, int);
node* preorder (node*);
node* inorder (node*);
node* postorder (node*);

node* create (node* root)
{
int no,ele,i=0;
node* n=NULL;
node *key;

printf("\nNumber of entries:\t");
scanf("%d", &no);

while (i<no)
{
printf("\n----INSERT----");
printf("\nEnter data:\t");
scanf("%d", &ele);
if (ele> 0)
{
key= search(root, ele);
if (key==NULL)
{
n=(node*)malloc(sizeof(node));
n->info = ele;
n->left=NULL; 
n->right=NULL;

if(root==NULL)
{
printf("\nIt's the first element of the tree.");
root=n;
}
else
{
insert(n, root);
}
i++;
}
else 
printf("The node data: %d already exists in the tree.",ele);
}
else printf("\nOnly Positive integers are allowed");
}
return root;
}


void insert (node* nw, node* root)
{
node *p;
node *q;
p=root; q=root;


while(q!=NULL)
{
p=q;

if(nw->info>q->info)
q=q->right;

else
q=q->left;
}

if(p->info > nw->info)
{
p->left = nw;
}
else
{
p->right = nw;
}
}


node* search(node* root, int ele)
{
node *q;
q=root;

while((q!=NULL)&&(q->info!=ele))
{
if(q->info>ele)
q=q->left;
else
q=q->right;
}
return q;
}


node* del(node* root, int ele)
{
node *temp, *r;
    if (root == NULL) return root;

    if (ele < root->info)
        root->left = del(root->left, ele);

    else if (ele > root->info)
        root->right = del(root->right, ele);

    else
    {
        if (root->left == NULL)
        {
            temp = root->right;
            free(root);
            return temp;
        }
        else if (root->right == NULL)
        {
            temp = root->left;
            free(root);
            return temp;
        }

  r=root->right;
  while(r->left!=NULL)
  r=r->left;
 
        temp = r;
        
        root->info = temp->info;

        root->right = del(root->right, temp->info);
    }
    return root;
}

node* preorder (node* q)
{

if(q!=NULL)
{
printf("  |  %d  |  ", q->info);
q->left = preorder(q->left);
q->right = preorder(q->right);
}
return q;
}


node* inorder (node* q)
{

if(q!=NULL)
{
q->left=inorder(q->left);
printf("  |  %d  |  ", q->info);
q->right=inorder(q->right);
}
return q;
}  

node* postorder (node* q)
{

if(q!=NULL)
{
q->left=postorder(q->left);
q->right=postorder(q->right);
printf("  |  %d  |  ", q->info);
}
return q;
}  

void main()
{
node *root=NULL, *q, *exist_or_not;
int choice, val, check=0, ele;


while(1)
{
printf("\n\n\n1. Create\n2. Search\n3. Delete a node.\n4. Preorder Traversal\n5. Inorder Traversal\n6. Postorder Traversal.\n7. Exit program.\n\nEnter your choice:\t");
scanf("%d", &choice);

switch(choice)
{
case 1: root=create(root); check=1; printf("\n\nCREATED"); break;

case 2: printf("Enter value to be searched:\t"); scanf("%d", &ele); q= search(root, ele); 
if(q==NULL) 
{
printf("\n%d doesn't exist in the tree.", ele);
}
else 
{
printf("\n%d found",q->info);
} break;

case 3: printf("Enter value to be deleted:\t"); 
scanf("%d", &val); exist_or_not= search(root, val); 
if(exist_or_not==NULL) 
printf("\nERROR: The value doesnot exist"); 
else 
root = del(root, val); break;


case 4: if(check) 
{   
preorder(root);
}
else 
printf("\nNo data stored yet, first create the tree."); break;


case 5: if(check) 
{ 
inorder(root);
} 
else 
printf("\nNo data stored yet, first create the tree."); break;


case 6: if(check)
{ 
 postorder(root);
 } 
 else 
 printf("\nNo data stored yet, first create the tree."); break;


       case 7: if(root==NULL) 
        printf("\nExiting with empty tree\n\n"); 
        else 
        {
        root->right=NULL; root->left=NULL; 
        free(root); 
        printf("\nFREED ROOT\n\n");
        } exit(0);

default: printf("\n\nHey!! Choose an option from the choices mentioned!!\n And stop testing my program!!");
}


}

}

-----------------------------------------------------------------------------------