programming-examples/c/Search_Sorting/C Program to Search for an Element in a Binary Search Tree.c

#include<stdio.h>
#include<stdlib.h>
struct node
{
    int info;
    struct node*left;
    struct node*right;
};
typedef struct node BST;
BST *LOC, *PAR;
void search(BST *root, int item)
{
    BST *save,*ptr;
    if (root == NULL)
        {
            LOC = NULL;
            PAR=NULL;
        }
    if (item == root -> info)
        {
            LOC = root;
            PAR = NULL;
            return;
        }
    if (item < root->info)
        {
            save = root;
            ptr = root->left;
        }
    else
        {
            save = root;
            ptr = root -> right;
        }
    while( ptr != NULL)
        {
            if (ptr -> info == item)
                {
                    LOC = ptr;
                    PAR = save;
                    return;
                }
            if(item < ptr->info)
                {
                    save = ptr;
                    ptr = ptr->left;
                }
            else
                {
                    save = ptr;
                    ptr = ptr->right;
                }
        }
    LOC = NULL;
    PAR = save;
    return;
}

struct node* findmin(struct node*r)
{
    if (r == NULL)
        return NULL;
    else if (r->left!=NULL)
        return findmin(r->left);
    else if (r->left == NULL)
        return r;
}
struct node*insert(struct node*r, int x)
{
    if (r == NULL)
        {
            r = (struct node*)malloc(sizeof(struct node));
            r->info = x;
            r->left = r->right = NULL;
            return r;
        }
    else if (x < r->info)
        r->left = insert(r->left, x);
    else if (x > r->info)
        r->right = insert(r->right, x);
    return r;
}

struct node* del(struct node*r, int x)
{
    struct node *t;
    if(r == NULL)
        printf("\nElement not found");
    else if (x < r->info)
        r->left = del(r->left, x);
    else if (x > r->info)
        r->right = del(r->right, x);
    else if ((r->left != NULL) && (r->right != NULL))
        {
            t = findmin(r->right);
            r->info = t->info;
            r->right = del(r->right, r->info);
        }
    else
        {
            t = r;
            if (r->left == NULL)
                r = r->right;
            else if (r->right == NULL)
                r = r->left;
            free(t);
        }
    return r;
}


int main()
{
    struct node* root = NULL;
    int x, c = 1, z;
    int element;
    char ch;
    printf("\nEnter an element: ");
    scanf("%d", &x);
    root = insert(root, x);
    printf("\nDo you want to enter another element :y or n");
    scanf(" %c",&ch);
    while (ch == 'y')
        {
            printf("\nEnter an element:");
            scanf("%d", &x);
            root = insert(root,x);
            printf("\nPress y or n to insert another element: y or n: ");
            scanf(" %c", &ch);
        }
    while(1)
        {
            printf("\n1 Insert an element ");
            printf("\n2 Delete an element");
            printf("\n3 Search for an element ");
            printf("\n4 Exit ");
            printf("\nEnter your choice: ");
            scanf("%d", &c);
            switch(c)
                {
                case 1:
                    printf("\nEnter the item:");
                    scanf("%d", &z);
                    root = insert(root,z);
                    break;
                case 2:
                    printf("\nEnter the info to be deleted:");
                    scanf("%d", &z);
                    root = del(root, z);
                    break;
                case 3:
                    printf("\nEnter element to be searched:  ");
                    scanf("%d", &element);
                    search(root, element);
                    if(LOC != NULL)
                        printf("\n%d Found in Binary Search Tree !!\n",element);
                    else
                        printf("\nIt is not present in Binary Search Tree\n");
                    break;
                case 4:
                    printf("\nExiting...");
                    return;
                default:
                    printf("Enter a valid choice: ");
                }
        }
    return 0;
}