BST not traversing - c++

My BST code is not showing any output and there is no error?
can someone please explain what I'm doing wrong?
I'm using Visual Code
I ran the code on multiple online compilers as well but just got a segmentation error and on vs code it's not showing anything at all.
#include <iostream>
#include <type_traits>
using namespace std;
class node
{
public:
int data;
node *left, *right;
node(int data){
this->data = data;
this->left = NULL;
this->right = NULL;
}
};
class BST{
public:
node* addNode(int data){
node* newNode = new node(data);
return newNode;
}
void Inorder(node* root){
if(root == NULL)
return;
Inorder(root -> left);
cout << root -> data << "\t";
Inorder(root -> right);
}
node* insert(node* newNode, int data){
if(newNode == NULL)
return addNode(data);
if(data < newNode -> data)
newNode -> left = insert(newNode, data);
else if(data > newNode -> data)
newNode -> right = insert(newNode, data);
return newNode;
}
};
int main(){
node *root = NULL;
BST objbst;
root = objbst.insert(root, 8);
root = objbst.insert(root, 3);
root = objbst.insert(root, 1);
root = objbst.insert(root, 6);
root = objbst.insert(root, 7);
root = objbst.insert(root, 10);
root = objbst.insert(root, 14);
root = objbst.insert(root, 4);
cout << "Inorder traversal: ";
objbst.Inorder(root);
}
if I'm doing something wrong then can someone please tell me what I'm doing wrong?

modify the insert function as given below and then run your code, you need to call left or right instances of node(based on condition) when traversing the tree recursively!
node* insert(node* Node, int data){
if(Node == NULL)
return addNode(data);
if(data < Node -> data)
Node -> left = insert(Node->left, data);
else if(data > Node -> data)
Node -> right = insert(Node->right, data);
return Node;
}

Related

Segmentation fault in Linked List code, deletion part

I am trying to code for insertion and deletion in linked list.
Here is my code for basic insertion and deletion of nodes in a singly linked list.
There are no errors in the code, but the output on the terminal shows segmentation fault. Can someone explain why am I getting a segmentation fault? And what changes do i make to remove the fault.
I believe the segmentation fault is in the deletion part. Please help.
// class is a type of user defined datatype
class Node {
public:
int data;
Node* next;
//constructor
Node(int data) {
this -> data = data;
this -> next = NULL;
}
// destructor
~Node() {
int value = this -> data;
//memory free krr rhe hain
if(this -> next != NULL){
delete next;
this -> next = NULL;
}
cout << "memory is free for node with data" << value << endl;
}
};
void insertAtHead(Node* &head, int data) {
// creating new node called temp of type Node
Node* temp = new Node(data);
temp -> next = head;
head = temp;
}
void insertAtTail(Node* &head, Node* &tail, int data) {
// //New node create
// Node* temp = new Node(data);
// tail -> next = temp;
// tail = temp;
Node* temp = new Node(data);
if (head == nullptr) { // If this is the first node of the list
head = temp;
} else { // Only when there is already a tail node
tail -> next = temp;
}
tail = temp;
}
void insertAtPosition(Node* &tail, Node* &head, int position, int data) {
// Insert at starting
if(position == 1) {
insertAtHead(head, data);
return;
}
// Code for inserting in middle
Node* temp = head;
int cnt = 1;
while(cnt < position-1) {
temp = temp -> next;
cnt++;
}
// Creating a node for data
Node* nodeToInsert = new Node(data);
nodeToInsert -> next = temp -> next;
temp -> next = nodeToInsert;
// Inserting at last position (tail)
if(temp -> next == NULL) {
insertAtTail(head,tail, data);
return;
}
}
void deleteNode(int position, Node* &head) {
//deleting first or starting node
if(position == 1) {
Node* temp = head;
head = head -> next;
//memory free start node
temp -> next = NULL;
delete temp;
} else {
// deleting any middle node
Node* curr = head;
Node* prev = NULL;
int cnt = 1;
while(cnt <= position) {
prev = curr;
curr = curr -> next;
cnt++;
}
prev -> next = curr -> next;
curr -> next = NULL;
delete curr;
}
}
void print(Node* &head) {
Node* temp = head;
while(temp != NULL) {
cout << temp -> data << " ";
temp = temp -> next;
}
cout << endl;
}
int main() {
Node* head = nullptr; // A list has a head
Node* tail = head; // a tail.
insertAtHead(head, 10); // pass the head
insertAtTail(head, tail, 20);
insertAtTail(head, tail, 30);
insertAtHead(head, 5);
print(head); // Print the whole list
cout << "head" << head -> data << endl;
cout << "tail" << tail -> data << endl;
deleteNode(1, head);
print(head);
}
The problem is not with the delete function since even commenting it out leads to segmentation fault.
The problem is that you are initializing tail = head which is set to nullptr at the start. However, when you insertAtHead, you set the value of head but leave the tail to nullptr. You need to do tail = head when adding the first node (when head == nullptr).
Refer below for working code:
// Online C++ compiler to run C++ program online
#include <iostream>
using namespace std;
// class is a type of user defined datatype
class Node {
public:
int data;
Node* next;
//constructor
Node(int data) {
this -> data = data;
this -> next = NULL;
}
// destructor
~Node() {
int value = this -> data;
//memory free krr rhe hain
if(this -> next != NULL){
delete next;
this -> next = NULL;
}
cout << "memory is free for node with data" << value << endl;
}
};
void insertAtHead(Node* &head,Node* &tail, int data) {
// creating new node called temp of type Node
Node* temp = new Node(data);
temp -> next = head;
if (head == nullptr)
tail = temp; //inializing tail
head = temp;
}
void insertAtTail(Node* &head, Node* &tail, int data) {
// //New node create
// Node* temp = new Node(data);
// tail -> next = temp;
// tail = temp;
Node* temp = new Node(data);
if (head == nullptr) { // If this is the first node of the list
head = temp;
} else { // Only when there is already a tail node
tail -> next = temp;
}
tail = temp;
}
void insertAtPosition(Node* &tail, Node* &head, int position, int data) {
// Insert at starting
if(position == 1) {
insertAtHead(head,tail, data);
return;
}
// Code for inserting in middle
Node* temp = head;
int cnt = 1;
while(cnt < position-1) {
temp = temp -> next;
cnt++;
}
// Creating a node for data
Node* nodeToInsert = new Node(data);
nodeToInsert -> next = temp -> next;
temp -> next = nodeToInsert;
// Inserting at last position (tail)
if(temp -> next == NULL) {
insertAtTail(head,tail, data);
return;
}
}
void deleteNode(int position, Node* &head) {
//deleting first or starting node
if(position == 1) {
Node* temp = head;
head = head -> next;
//memory free start node
temp -> next = NULL;
delete temp;
} else {
// deleting any middle node
Node* curr = head;
Node* prev = NULL;
int cnt = 1;
while(cnt <= position) {
prev = curr;
curr = curr -> next;
cnt++;
}
prev -> next = curr -> next;
curr -> next = NULL;
delete curr;
}
}
void print(Node* &head) {
Node* temp = head;
while(temp != NULL) {
cout << temp -> data << " ";
temp = temp -> next;
}
cout << endl;
}
int main() {
Node* head = nullptr; // A list has a head
Node* tail = head; // a tail.
insertAtHead(head,tail, 10); // pass the head
insertAtTail(head, tail, 20);
insertAtTail(head, tail, 30);
insertAtHead(head,tail, 5);
print(head); // Print the whole list
cout << "head" << head -> data << endl;
cout << "tail" << tail -> data << endl;
deleteNode(1, head);
print(head);
}
The segfault is actually in the function insertAtTail(), and is because, while you handle the case where head is a null pointer, you do not handle the case where there is a head node but no tail node. The following code fixes this issue:
void insertAtTail(Node* &head, Node* &tail, int data) {
// //New node create
Node* temp = new Node(data);
if (head == nullptr) { // If this is the first node of the list
head = temp;
} else if (tail == nullptr) { // if there's a head but no tail
head -> next = temp;
} else { // Only when there is already a tail node
tail -> next = temp;
}
tail = temp;
}
If you have a look at this part of your code:
int main()
{
Node* head = nullptr; // A list has a head
Node* tail = head; // a tail.
insertAtHead(head, 10); // pass the head
insertAtTail(head, tail, 20);
return 0;
}
tail is a nullptr as you pass it into insertAtTail(head, tail, 20);
Then in insertAtTail you are going to access this nullptr:
void insertAtTail(Node* &head, Node* &tail, int data) {
// //New node create
// Node* temp = new Node(data);
// tail -> next = temp;
// tail = temp;
Node* temp = new Node(data);
if (head == nullptr) {
head = temp;
} else {
// here you have nullptr access resulting in your segmentation fault
tail -> next = temp;
}
tail = temp;
}

Searching for an object inside a binary search tree

**The trace function is the one I am using to search through the binary search tree it returns the right order of numbers when I search for something within the tree but when I want to see if a number doesn't exist i get segmentation fault **
// Binary search tree
#include <stdio.h>
#include <iostream>
#include <assert.h>
using namespace std;
struct node
{
int data;
node * left;
node * right;
};
node * newNode(int data){
node * newnode = new node();
newnode -> data = data;
newnode -> left = NULL;
newnode -> right = NULL;
return newnode;
}
node* Insert (node * root, int data){
if(root == NULL){
root = newNode(data);
}
else if(data <= root-> data){
root->left = Insert(root->left, data);
}
else{
root -> right = Insert(root->right, data);
}
return root;
};
int Trace(node* root,int find){
node * searcher = root;
if(searcher->data == find){
cout << searcher->data << endl;
}
else if(find <= root -> data){
Trace(searcher->left, find);
cout << searcher ->data<< endl;
}
else if(find >= root -> data){
Trace(searcher->right, find);
cout << searcher ->data << endl;
}
else cout << "not found" << endl;
return searcher-> data;
};
int main(){
node * root = NULL; // creating an empty tree
root = Insert(root, 234234);
root = Insert(root, 2334);
root = Insert(root, 23784);
root = Insert(root, 223);
root = Insert(root, 4244);
root = Insert(root, 673234);
root = Insert(root, 2);
root = Insert(root, 2344);
root = Insert(root, 234);
Trace(root,4244);
return 0;
}
When you are walking through the tree looking for a member that doesn't exist, you'll eventually reach a NULL node. When you try to assess its data, you get a segmentation fault. You can avoid this by checking if the node you are going to assess is valid. For example, change your function Trace to:
int Trace(node* root, int find) {
node * searcher = root;
if(!searcher) {
cout << "Node not found" << endl;
//return something here
}
//rest of function stays the same
}

C++ program implementing tree stops working when a node is inserted and I can't understand why

here is my code. after reading T the program reads the first input data and stops working. message "Unhandled exception at 0x00844D30 in tree.exe: 0xC0000005: Access violation reading location 0x00000000." is shown. I included iostream and stddef.h libraries.
class Node{
public:
int data;
Node *left, *right;
Node(int d){
data = d;
left = right = NULL;
}
};
class Solution{
public:
Node* insert(Node* root, int data){
if (root = NULL){
return new Node(data);
}
else{
Node* cur;
if (data <= root->data){
cur = insert(root->left, data);
root->left = cur;
}
else{
cur = insert(root->right, data);
root->right = cur;
}
return root;
}
}
};
int main(){
Solution myTree;
Node* root = NULL;
int T, data;
cin >> T;
while (T-->0){
cin >> data;
root = myTree.insert(root, data);
}
return 0;
}
This if will always go into the else part. Because you assign NULL to the variable root and then check the value. It should be root == NULL
if (root = NULL){
return new Node(data);
}
else{
Node* cur;
if (data <= root->data){
cur = insert(root->left, data);
root->left = cur;
}
else{
cur = insert(root->right, data);
root->right = cur;
}
return root;
}
The condition should be
if (root==NULL)
#include <iostream>
#include <stddef.h>
using namespace std;
class Node{
public:
int data;
Node *left, *right;
Node(int d){
data = d;
left = right = NULL;
}
};
class Solution{
public:
Node* insert(Node* root, int data){
if(root == NULL){
return new Node(data);
}
else{
Node* cur;
if (data <= root->data){
cur = insert(root->left, data);
root->left = cur;
}
else{
cur = insert(root->right, data);
root->right = cur;
}
cur->left=cur->right=NULL;
return root;
}
}
};
int main(){
Solution myTree;
Node* root = NULL;
int T, data;
cin>>T;
while (T-->0){
cin>>data;
root = myTree.insert(root, data);
}
return 0;
}

Segmentation Fault coming "Insertion in Binary Search tree." #

I am writing a function to insert a node in BST,but getting segmentation fault.
/*
Node is defined as
typedef struct node
{
int data;
node * left;
node * right;
}node;
*/
node * findPos(node * tree, int value){
if(tree -> data > value){
return findPos(tree -> left, value);
}
else if (tree -> data < value){
return findPos(tree -> right, value);
}
return tree;
}
node * addNode(int value){
struct node * temp =(struct node *)malloc(sizeof(struct node));
temp->data = value;
temp->left = NULL;
temp -> right = NULL;
return temp;
}
node * insert(node * root, int value)
{
node * ptr = root;
if(ptr == NULL)
return addNode(value);
else if(ptr -> data > value){
ptr->left = findPos(ptr -> left, value);
}
else if(ptr -> data < value){
ptr->right = findPos(ptr -> right, value);
}
return root;
}
i am not able to understand which illegal memory i am trying to access which is giving this error.
Please help me with this.
Thanks in advance :)
Thanks for the help guys!!!
got the program working
/*
Node is defined as
typedef struct node
{
int data;
node * left;
node * right;
}node;
*/
node * addNode(int value){
struct node * temp =(struct node *)malloc(sizeof(struct node));
temp->data = value;
temp->left = NULL;
temp -> right = NULL;
return temp;
}
node * insert(node * root, int value)
{
node * ptr = root;
if(ptr == NULL)
return addNode(value);
else if(ptr -> data > value){
ptr->left = insert(ptr -> left, value);
}
else if(ptr -> data < value){
ptr->right = insert(ptr -> right, value);
}
return root;
}
There are two issues here:
findPos should handle the case in which tree is NULL.
insert should not recursively call findPos. Instead it should recursively call insert. Something like this (haven't tested it):
node * insert(node * root, int value)
{
node * ptr = root;
if(ptr == NULL)
return addNode(value);
else if(ptr -> data > value) {
return insert(ptr -> left, value);
} else if(ptr -> data < value) {
return insert(ptr -> right, value);
} else
return root;
}

Iterative BST insertion in C++

I am trying to understand BSTs and how to insert elements into it iteratively. My node structure implementation looks like so:
struct Node{
Node *left;
Node *right;
T data; //template class
};
And my insertion implementation looks like so:
template<typename T>
bool BST<T>::Insert(const T value)
{
Node *newNode = new Node;
newNode -> data = value;
newNode -> left = NULL;
newNode -> right = NULL;
if(root == NULL) {root = newNode;} //If the BST is empty
else
{//The BST is not empty
Node *ptr = root; //points to the current Node
Node *ptr_parent; //points to the parent Node
while(ptr != NULL)
{
if((ptr -> data) > value)
{
ptr_parent = ptr;
ptr = ptr -> left;
}
if((ptr -> data) < value)
{
ptr_parent = ptr;
ptr = ptr -> right;
}
}
}
ptr = newNode; //insert the newNode at the spot
if((ptr_parent -> data) < value)
ptr_parent -> right = newNode;
else
ptr_parent -> left = newNode;
return true;
}
The insertion works when adding the first Node into an empty tree but I get a segmentation fault whenever i try to add more Nodes. I understand that there are posts that show how to implement insertions into BSTs but most of them show the recursive method, and those with iterative examples are incomplete or too specific. Thank you.
I think I'd do things a little differently. First, I'd simplify the other code a little by adding a ctor to the Node class:
struct Node{
Node *left;
Node *right;
T data;
Node(T const &data) : left(nullptr), right(nullptr), data(data) {}
};
Then you can use a pointer to a pointer to traverse the tree and insert the item:
bool insert(const T value) {
Node **pos;
for (pos = &root; *pos != nullptr;) {
if (value < (*pos)->value)
pos = &(*pos)->left;
else if ((*pos)->value < value )
pos = &(*pos)->right;
else
return false;
}
*pos = new Node(value);
return true;
}
Note that I've delayed creating the new node until after we've dropped out of the loop. This way, if we have a duplicate element, we can just return (without leaking a node, since we haven't allocated a new node yet).
For what it's worth, if you were going to do this recursively, it would probably be easier to use a reference to a pointer instead of a pointer to a pointer.
I was able to make my original code work last night, I'm sharing the answer here:
template<typename T>
bool BST<T>::Insert(const T value)
{
Node *ptr;
Node *ptr_parent;
if(root == NULL)
{//The BST is Empty...
Node *newNode = new Node;
newNode -> data = value;
newNode -> left = NULL;
newNode -> right = NULL;
root = newNode;
ptr = root;
} else { //traversing the tree to find the insertion point
ptr = root;
while(ptr != NULL)
{
if((ptr -> data) == value) {return false;} //to check for duplicates
if(value < (ptr -> data))
{
ptr_parent = ptr;
ptr = ptr -> left;
} else {
ptr_parent = ptr;
ptr = ptr -> right;
}
}
Node *newNode = new Node;
newNode -> data = value;
newNode -> left = NULL;
newNode -> right = NULL;
//checking for parent value to determine if
//the Node is a left or right child
if(value < (ptr_parent -> data))
ptr_parent -> left = newNode;
else
ptr_parent -> right = newNode;
}
++count;//to keep track of the Node count
return true;
}
For my own sake I wanted to solve this without using double pointers.
You didn't handle the case when ptr->data == value so the loop will be infinite whenever a duplicate is found, and ptr = newNode doesn't do anything, it just makes ptr point to newNode. Try this
//ptr holds the address of pointers to nodes.
Node **ptr = &root;
while(*ptr != NULL){
if((*ptr)->data > T)
ptr = &(*ptr)->right;
else
ptr = &(*ptr)->left;
//Not handling duplicates
}
//Change the value of the pointer to newNode
*ptr = newNode;
Use hard pointers
Node **ptr = &root; //points to the current Node
Node **ptr_parent; //points to the parent Node
When you are trying to do this
ptr = newNode; //insert the newNode at the spot
it doesn't do anyithing because you need to modify the pointer which points to the left or the right subnode
something like this:
template<typename T>
bool BST<T>::Insert(const T value)
{
Node *newNode = new Node;
newNode -> data = value;
newNode -> left = NULL;
newNode -> right = NULL;
if(root == NULL) {root = newNode;} //If the BST is empty
else
{//The BST is not empty
Node **ptr = &root; //points to the current Node
Node **ptr_parent; //points to the parent Node
while((*ptr) != NULL)
{
if(((*ptr) -> data) > value)
{
ptr_parent = ptr;
ptr = &ptr -> left;
}
if(((*ptr) -> data) < value)
{
ptr_parent = ptr;
ptr = &ptr -> right;
}
}
}
(*ptr) = newNode; //insert the newNode at the spot
if(((*ptr_parent) -> data) < value)
(*ptr_parent) -> right = newNode;
else
(*ptr_parent) -> left = newNode;
return true;
}
As I understand, it is failing because of following line:
ptr = newNode; //insert the newNode at the spot
after the while loop your ptr is NULL otherwise you can not exit from the while loop. You are assigning a struct to NULL, which is not right.
Hopefully this helps. Everything else looks normal.
void insert(node* root, int value)
{
if (root == NULL)
{
root = new node;
root->data = value;
return;
}
while(!((root->data < value && root->right == NULL) || (root->data >= value && root->left == NULL)))
{
if (root->data < value)
root = root->right;
else
root = root->left;
}
if (root->data < value)
{
root->right = new node;
root->right->data = value;
} else
{
root->left = new node;
root->left->data = value;
}
}
template <class T>
class TreeNode{
private:
T data;
TreeNode<T>* right,*left;
public:
void setData(T d){
this->data =d;
}
T getData(){
return this->data;
}
void setRight(TreeNode<T>* r){
this->right =r;
}
TreeNode<T>* getRight(){
return this->right;
}
void setLeft(TreeNode<T>* r){
this->left =r;
}
TreeNode<T>* getLeft(){
return this->left;
}
static TreeNode<T>* newNode(T data){
TreeNode<T>* n = new TreeNode<T>();
n->setData(data);
n->setRight(NULL);
n->setLeft(NULL);
return n;
}
};
template <class T>
class BinaryTree{
private:
TreeNode<T>* root;
public:
void insert(T data){
TreeNode<T>* n = TreeNode<T>::newNode(data);
if(root==NULL)
root = n;
else{
TreeNode<T>* t = root;
while(t!=NULL){
if(n->getData() >= t->getData()){
if(t->getRight()==NULL){
t->setRight(n); //newnode attached as right child in tree
t = NULL;
}
else
t = t->getRight();
}
else{
if(t->getLeft()==NULL){
t->setLeft(n); //newnode attached as left child in tree
t=NULL;
}
else
t = t->getLeft();
}
}
}
}
void preorder(){
TreeNode<T>* t = root;
preorderUtil(t);
}
void preorderUtil(TreeNode<T>* node){
if(node==NULL)
return;
preorderUtil(node->getLeft());
cout<<node->getData()<<" ";
preorderUtil(node->getRight());
}
};
I answered a case here Binary Search Tree insertion doesn't work see if it helps
void insert(int val)
{
Node *newNode;
newNode=new Node;
newNode->data=val;
Node *currentNode=root;
Node *parentNode;
if(root==NULL)
{
newNode->left=NULL;
newNode->right=NULL;
}
else
{
while(currentNode!=NULL)
{
if((currentNode->data)>val)
{
parentNode=currentNode;
currentNode=currentNode->left;
}
if((currentNode->data)<val)
{
parentNode=currentNode;
currentNode=currentNode->right;
}
}
}
currentNode=newNode;
if((parentNode->data)<val)
{
parentNode->right=newNode;
}
else
{
parentNode->right=newNode;
}
}