tree-1

#include <iostream>

void leftView(Node *root)
{
    std::queue<Node*>q;
    q.push(root);
    q.push(NULL);
    while(!q.empty()){
        Node* tmp = q.front();
        if(tmp!=NULL)
        std::cout<<tmp->data<<" ";
        while(q.front()!=NULL){
            if(q.front()==NULL)
                q.pop();
            if(tmp->left)
                q.push(tmp->left);
            if(tmp->right)
                q.push(tmp->right);
            q.pop();
            tmp = q.front();
        }
        q.pop();
        if(!q.empty())
        q.push(NULL);
   }
}

void leftViewBFSUtil(Node* root,int n){
    leftViewBFS(root,0,1);
}
void leftViewBFS(Node *root,int &r,int h)
{
    if(root==NULL)
    return;
    
    if(r<h){
          std::cout<<root->data<<" ";
          r=h;
    }
    leftViewBFS(root->left,r,h+1);
    leftViewBFS(root->right,r,h+1);
}

bool isBST(Node* root) {
    if(root==NULL)
    return true;
    
    static Node* prev=NULL;
    isBST(root->left);
    if(prev==NULL)
    prev=root;
    else{
      //  std::cout<<prev->data<<" "<<root->data<<"\n";
        if(prev->data>root->data)
        return false;
        prev=root;
    }
    isBST(root->right);
    
    return true;
    
}

int main()
{
    
    return 0;
}