15_BST.c

//Aim:Write a program to implement traversal, insertion and deletion operations in Binary Search Tree.
//Code

#include <stdlib.h>
struct btnode
{
    int value;
    struct btnode *l;
    struct btnode *r;
}*root = NULL, *temp = NULL, *t2, *t1;
 
void delete1();
void insert();
void delete();
void inorder(struct btnode *t);
void create();
void search(struct btnode *t);
void search1(struct btnode *t,int data);
int smallest(struct btnode *t);
int largest(struct btnode *t);
 
int flag = 1;
 
void main()
{
    int ch,n,i;

    printf("\nOPERATIONS ---");
    printf("\n1 - Create Binary Search Tree\n");
    printf("2 - Insert an element into tree\n");
    printf("3 - Delete an element from the tree\n");
    printf("4 - Inorder Traversal\n");
    printf("5 - Exit\n");
    while(1)
    {
        printf("\nEnter your choice : ");
        scanf("%d", &ch);
        switch (ch)
        {
        case 1:  
        printf("Enter number of elements to be inserted = ");
        scanf("%d", &n);
         for (i = 0; i < n; i++) 
{
            insert();}
            printf("\nThe Binary Search Tree = ");
            inorder(root);
            break;
        case 2:
        insert();
        break;
        case 3:    
            delete();
            break;
        case 4:    
            inorder(root);
            break;
        case 5:    
            exit(0);
        default :     
            printf("Wrong choice, Please enter correct choice  ");
            break;    
        }
    }
}

void insert()
{
    create();
    if (root == NULL) 
        root = temp;
    else    
        search(root);    
}
 
void create()
{
    int data;
 
    printf("Enter data of node to be inserted : ");
    scanf("%d", &data);
    temp = (struct btnode *)malloc(1*sizeof(struct btnode));
    temp->value = data;
    temp->l = temp->r = NULL;
}
 
void search(struct btnode *t)
{
    if ((temp->value > t->value) && (t->r != NULL))      
        search(t->r);
    else if ((temp->value > t->value) && (t->r == NULL))
        t->r = temp;
    else if ((temp->value < t->value) && (t->l != NULL))   
        search(t->l);
    else if ((temp->value < t->value) && (t->l == NULL))
        t->l = temp;
}

void inorder(struct btnode *t)
{
    if (root == NULL)
    {
        printf("No elements in a tree to display");
        return;
    }
    if (t->l != NULL)    
        inorder(t->l);
    printf("%d -> ", t->value);
    if (t->r != NULL)    
        inorder(t->r);
}
 
void delete()
{
    int data;
 
    if (root == NULL)
    {
        printf("No elements in a tree to delete");
        return;
    }
    printf("Enter the data to be deleted : ");
    scanf("%d", &data);
    t1 = root;
    t2 = root;
    search1(root, data);
}

void search1(struct btnode *t, int data)
{
    if ((data>t->value))
    {
        t1 = t;
        search1(t->r, data);
    }
    else if ((data < t->value))
    {
        t1 = t;
        search1(t->l, data);
    }
    else if ((data==t->value))
    {
        delete1(t);
    }
}
 

void delete1(struct btnode *t)
{
    int k;
 
    if ((t->l == NULL) && (t->r == NULL))
    {
        if (t1->l == t)
        {
            t1->l = NULL;
        }
        else
        {
            t1->r = NULL;
        }
        t = NULL;
        free(t);
        return;
    }

    else if ((t->r == NULL))
    {
        if (t1 == t)
        {
            root = t->l;
            t1 = root;
        }
        else if (t1->l == t)
        {
            t1->l = t->l;
 
        }
        else
        {
            t1->r = t->l;
        }
        t = NULL;
        free(t);
        return;
    }
 
    else if (t->l == NULL)
    {
        if (t1 == t)
        {
            root = t->r;
            t1 = root;
        }
        else if (t1->r == t)
            t1->r = t->r;
        else
            t1->l = t->r;
        t == NULL;
        free(t);
        return;
    }
 
    else if ((t->l != NULL) && (t->r != NULL))  
    {
        t2 = root;
        if (t->r != NULL)
        {
            k = smallest(t->r);
            flag = 1;
        }
        else
        {
            k =largest(t->l);
            flag = 2;
        }
        search1(root, k);
        t->value = k;
    }
 
}
 
int smallest(struct btnode *t)
{
    t2 = t;
    if (t->l != NULL)
    {
        t2 = t;
        return(smallest(t->l));
    }
    else    
        return (t->value);
}

int largest(struct btnode *t)
{
    if (t->r != NULL)
    {
        t2 = t;
        return(largest(t->r));
    }
    else    
        return(t->value);
}