Binary Tree Implementation

what is tree??

In computer science, a tree is a widely used abstract data type (ADT) or data structure implementing this ADT that simulates a hierarchical tree structure, with a root value and subtrees of children with a parent node, represented as a set of linked nodes.

Program:

#include <iostream> 
#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<<" "; 
} 
}