Data Structures using C++

  #include<iostream> 
  #include<stdlib.h> 
using namespace std;
  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<<" "; 
     } 
   }