binary_tree.cpp

#include<bits/stdc++.h>
using namespace std;

class node{
    public:
    int data;
    node* left;
    node* right;


node(int d){
    this->data=d;
    this->left=NULL;
    this->right=NULL;
}
};

node* buildTree(node* root){
    cout<<"Enter data: "<<endl;
    int data;
    cin>>data;

    root=new node(data);

    if(data==-1)
    return NULL;

    cout<<"Enter the data for inserting in left of  "<<data<<endl;
    root->left=buildTree(root->left);
    cout<<"Enter the data for inserting in right of "<<data<<endl;
    root->right= buildTree(root->right);

    return root;
}


void levelOrderTraversal(node* root){
    queue<node*> q;

    q.push(root);
    q.push(NULL);

    while(!q.empty()){
        node* temp=q.front();
        q.pop();

        if(temp==NULL){
            //purana vala level completely traverse ho chuka h
            cout<<endl;
            if(!q.empty()){
                //queue still has some child nodes
                q.push(NULL);
            }
        }

            else{
                cout<<temp->data<<" ";

                if(temp->left){
                    q.push(temp->left);
                }

                if(temp->right){
                    q.push(temp->right);
                }
            }
        }
    }


void inorder(node* root){
    //base case
    if(root==NULL){
        return;
    }

    inorder(root->left);
    cout<<root->data<<" ";
    inorder(root->right);

}


void preorder(node* root){
    //base case
    if(root==NULL){
        return;
    }
    cout<<root->data<<" ";
    preorder(root->left);
    preorder(root->right);
}

void postorder(node* root){
    //base case
    if(root==NULL){
        return;
    }

    postorder(root->left);
    postorder(root->right);
    cout<<root->data<<" ";
}

void buildFromLevelOrder(node* &root) {
    queue<node*> q;

    cout << "Enter data for root" << endl;
    int data ;
    cin >> data;
    root = new node(data);
    
    q.push(root);

    while(!q.empty()) {
        node* temp = q.front();
        q.pop();

        cout << "Enter left node for: " << temp->data << endl;
        int leftData;
        cin >> leftData;

        if(leftData != -1) {
            temp -> left = new node(leftData);
            q.push(temp->left);
        }

        cout << "Enter right node for: " << temp->data << endl;
        int rightData;
        cin >> rightData;

        if(rightData != -1) {
            temp -> right = new node(rightData);
            q.push(temp->right);
        }
    }
 }

int main(){

    node* root=NULL;

    //creating a tree
    root=buildTree(root);

cout<<endl;

    //LEVEL ORDER TRAVERSAL
     cout << "Printing the level order traversal output " << endl;
    levelOrderTraversal(root);    

cout<<endl;

    cout << "inorder traversal is:  ";
    inorder(root); 
    cout << endl << "preorder traversal is:  ";
    preorder(root); 
    cout << endl << "postorder traversal is:  ";
    postorder(root); 
                

return 0;
}