Binary tree

#include <iostream>

using namespace std;

struct  node
{
   node* leftchild;
   node* rightchild;
   int data;
};

int count;

node* insert(node*ptr,int x)
{ 
     if(ptr==NULL)
       {
          node* temp= new node;
          temp->leftchild=NULL;
          temp->rightchild=NULL;
          temp->data=x;
          ptr=temp;
          count++;
       }
      else if(count%2==0)
          ptr->leftchild=insert(ptr->leftchild,x);

      else
          ptr->rightchild=insert(ptr->rightchild,x);

return ptr;

}

void preorder(node* root)
{
    if(root!=NULL)
{
    cout<<root->data<<endl;
    preorder(root->leftchild);
    preorder(root->rightchild);

}
}

void inorder(node *root)
{
    if (root!= NULL)
    {
        inorder(root->leftchild);
        cout<<root->data<<endl;
        inorder(root->rightchild);
    }
}

void postorder( node *root)
{
    if (root != NULL)
    {
        postorder(root->leftchild);

        postorder(root->rightchild);
        cout<<root->data<<endl;
    }
}

int main()
{
    count=0;int x;
    node* root=NULL;

    char ch='y';
    while(ch!='n')
    {
        cout<<"Enter the element:";
        cin>>x;
        root=insert(root,x);
        cout<<"Do you want to enter more elements? y/n";
        cin>>ch;
    }

cout<<"Preorder traversal:";
preorder(root);
cout<<"Inorder traversal:";
inorder(root);
cout<<"Postorder traversal";
postorder(root);
}

Binary search tree

#include <iostream>

using namespace std;
struct node
{
    int data;
     node* left;
     node* right;
};

void preorder(struct node *root)
{
    if (root != NULL)
    {   cout<<root->data<<endl;
        preorder(root->left);

        preorder(root->right);
    }
}
void inorder(struct node *root)
{
    if (root != NULL)
    {
        inorder(root->left);
        cout<<root->data<<endl;
        inorder(root->right);
    }
}

void postorder(struct node *root)
{
    if (root != NULL)
    {
        postorder(root->left);

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

node* insert(node* ptr, int x)
{

    if (ptr == NULL)
       {
            node* temp =  new node;

            temp->data = x;
            temp->left = temp->right = NULL;
            ptr=temp;

       }

    else  if (x < ptr->data)
        ptr->left  = insert(ptr->left,x);
    else if (x> ptr->data)
        ptr->right = insert(ptr->right,x);

    return ptr;
}
int main()
{int x;

    struct node *root = NULL;
    char ch='y';
    while(ch!='n')
    {
        cout<<"Enter the element:";
        cin>>x;
        root= insert(root,x);
        cout<<"Do you want to insert more elements y/n:";
        cin>>ch;

    }

cout<<"Preorder traversal:";
preorder(root);
cout<<"Inorder traversal:";
inorder(root);
cout<<"Postorder traversal";
postorder(root);

    return 0;
}

Simple calculator using switch case

#include <iostream>

using namespace std;

int main()
{long first,second;
char ch;
cout<<"ENTER FIRST INTEGER:";
cin>>first;
cout<<"ENTER SECOND INTEGER";
cin>>second;
cout<<"ENTER THE OPERAND";
cin>>ch;
switch(ch)
{
     case '+' : cout<<"THE SUM IS:"<<first +second;
                break;
     case '-' : cout<<"THE DIFFERENCE IS:"<<first -second;
                break;
     case '/' : cout<<"THE QUOTIENT IS:"<<first/second;
                cout<<"THE REMAINDER IS:"<<first%second;
                break;
     case '*' : cout<<"THE PRODUCT IS:"<<first*second;
                break;

}

}