Tree.c

#include<stdio.h>
#include <stdlib.h>
struct node{
    int data;
    struct node*left;
    struct node*right;
};
struct node* createnode(int data){
    struct node *n;
    n = (struct node*)malloc(sizeof(struct node));
    n->data = data;
    n->left = NULL;
    n->right =NULL;
    return n;
}
int isBST(struct node* root){
    static struct node* prev = NULL;
    if(root != NULL){
        if(!isBST(root->left)){
            return 0;
        }
        if(prev != NULL && root->data <= prev->data){
            return 0;
        }
        prev = root;
        return isBST(root->right);
    }
        else{
            return 1;
        }
    
}

struct node* search(struct node* root , int key){
    if(root == NULL){
        return NULL;
    }
    if(key == root->data){
        return root;
    }
    else if ( key<root->data){
        return search(root->left, key);
    }
    else{
        return search(root->right, key);
    }
}

struct node* iterativesearch(struct node* root , int key){
    while(root!=NULL){
   if(key == root->data){
    return root;
   }
   else if(root-> data > key){
    return iterativesearch(root ->left, key);
   }
   else{
    return iterativesearch(root->right, key);
       }
    }
}
void insertion(struct node* root, int val){
    struct node*prev = NULL;
    while(root!=NULL){
        prev = root;
        if(val == root->data){
            return;
        }
        else if (val> root->data){
            root = root->right ;
        }
        else {
            root = root->left;
        }
    }
    struct node* new = createnode(val);
    if(val <prev ->data){
        prev->left=new;
    }
    else {
        prev->right =new;
    }
}
struct node*inorderpredeccor(struct node*root){
    root = root->left;
    while(root->right != NULL){
        root = root -> right;
    }
}
struct node* deletion(struct node*root, int key){
    struct node* ipre;
    if(root == NULL){
        return NULL;
    }
    if(root->left == NULL&&root->right == NULL){
        free(root);
        return NULL;
    }
    if(key < root->data){
        root -> left = deletion(root -> left,key);
    }
    else if(key > root->data){
        root -> left = deletion(root -> right,key);
        }
    else{
        ipre = inorderpredeccor(root);
        root->data=ipre->data;
        root -> left = deletion(root->left,ipre->data);
    }    
    return root; 
   }
int main (){
    struct node*p= createnode(4);
    struct node*p1= createnode(3);
    struct node*p2= createnode(6);
    struct node*p3= createnode(5);
    struct node*p4= createnode(11);
    p->left = p1;
    p->right =p2; 
    p2->left = p3;
    p2->right = p4;
    insertion(p,1);
    struct node * n = search(p,1);
    if(n != NULL){
    printf("Found %d it exists: ", n->data );
    }
    else{
        printf("Element not found");
    }
    printf("\n");
    deletion(p,1);
    struct node * t = search(p,1);
    if(t != NULL){
    printf("Found %d it exists: ", t->data );
    }
    else{
        printf("Element not found");
    }
    return 0;
}