Data Structures - Binary Tree Implementation

  #include < iostream.h >
  #include < conio.h >
  #include < stdlib.h >
  struct node
  {
    node *left;
    int value;
    node *right;
  };
  node *curr=NULL;
  int addnode(node *, node *);
  int inorder(node *);
  int preorder(node *);
  int postorder(node *);
  void main()
  {
     char c;
     int v;
     clrscr();
     do
     {
       cout<<"Select any one";
       cout<<"0 ->Exit";
       cout<<"1 ->Add node";
       cout<<"2 ->Inorder traversal";
       cout<<"3 ->Preorder traversal";
       cout<<"4 ->Postorder trversal :";
       cin>>c;
       switch(c)
       {
         case '0':
           exit(1);
         case '1':
           node *temp;
           temp = new node;
           cout<<" Enter the value of the node : ";
           cin>>temp->value;
           if(curr==NULL)
           {
             curr=new node;
             curr->value=temp->value;
             curr->left=NULL;
             curr->right=NULL;
             cout<<" The root node is added";
           }
           else
             v=addnode(curr,temp);
           if(v==1)
             cout<<" The node is added to the left";
           else if(v==2)
             cout<<" The node is added to the right";
           else if(v==3)
             cout<<" The same value exists";
           break;
         case '2':
           v=inorder(curr);
           if(v==0)
             cout<<"The tree is empty";
           break;
         case '3':
           v=preorder(curr);
           if(v==0)
             cout<<"The tree is empty";
           break;
         case '4':
           v=postorder(curr);
           if(v==0)
             cout<<"The tree is empty";
           break;
         default:
           cout<<"Invalid entry";
           break;
       }
     }while(c!='0');
     getch();
  }
  int addnode(node *fcurr, node *fnew )
  {
     if(fcurr->value==fnew->value)
     {
       return 3;
     }
     else
     {
       if(fcurr->value > fnew->value)
       {
         if(fcurr->left != NULL)
           addnode(fcurr->left, fnew);
         else
         {
           fcurr->left = fnew;
           (fcurr->left)->left=NULL;
           (fcurr->left)->right=NULL;
           return 1;
         }
       }
       else
       {
         if(fcurr->right != NULL)
           addnode(fcurr->right, fnew);
         else
         {
           fcurr->right = fnew;
           (fcurr->right)->left=NULL;
           (fcurr->right)->right=NULL;
           return 2;
         }
       }
     }
  }
  int inorder(node *fincurr)
   {
     if(fincurr == NULL)
       return 0;
     else
     {
       if(fincurr->left != NULL)
         inorder(fincurr->left);
         cout << fincurr->value<<" ";
       if(fincurr->right != NULL)
         inorder(fincurr->right);
     }
   }
  int preorder(node *fprcurr)
   {
     if(fprcurr == NULL)
       return 0;
     else
     {
       cout << fprcurr->value<<" ";
       if(fprcurr->left != NULL)
         preorder(fprcurr->left);
       if(fprcurr->right != NULL)
         preorder(fprcurr->right);
     }
   }
  int postorder(node *fpocurr)
   {
     if(fpocurr == NULL)
       return 0;
     else
     {
       if(fpocurr->left != NULL)
         postorder(fpocurr->left);
       if(fpocurr->right != NULL)
         postorder(fpocurr->right);
       cout << fpocurr->value<<" ";
     }
   }