# Binary Tree Traversals in C++

In this tutorial, we will learn Binary tree traversals in C++. Three standard ways to traverse a binary tree T with root R are preorder, inorderpostorder, are as follows:

Preorder:

1. Process root R.
2. Travel in the left subtree of R in preorder.
3. Travel in the right subtree of R in preorder.

Inorder:

1. Travel in left subtree of R in inorder.
2. Process root R.
3. Travel in right subtree of R in inorder.

Postorder:

1. Travel in left subtree of R in postorder.
2. Travel in right subtree of R in postorder.
3. Process  root R.

The three algorithm are sometimes called , respectively , the node-left-right(NLR) traversal ,the left-node-right(LNR) traversal and the left-right-root(LRN) traversal.

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## Program: Perform Binary Tree Traversals in C++

Below is the C++ Code to perform the mentioned operation.

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

struct st
{
int data;
struct st *left;
struct st *right;
};
struct st *root=NULL,*temp;
void insertElements();
void preorder(struct st *);
void inorder(struct st *);
void postorder(struct st *);
int main()
{
int ch;

while(1)
{
cout<<"\n 1.insert Elements \n 2.preorder \n 3.inorder \n 4.postorder \n5.exit";
cout<<"\n enter ur choice ";
cin>>ch;
switch(ch)
{
case 1:insertElements();break;
case 2:preorder(root);break;
case 3:inorder(root);break;
case 4:postorder(root);break;
case 5:exit(1);break;
default:cout<<"invalid operation";

}
}
}
void insertElements()
{
struct st *nc,*pNode;
int v;
cout<<"\n enter the value ";
cin>>v;
temp=new st;
temp->data=v;
temp->left=NULL;
temp->right=NULL;
if(root==NULL)
{
root=temp;
}
else
{
nc=root;
while(nc!=NULL)
{
pNode=nc;
if(v<nc->data)
nc=nc->left;
else
nc=nc->right;
}
if(v<pNode->data)
{
pNode->left=temp;
}
else
pNode->right=temp;
}
}
void preorder(struct st *temp)
{
if(temp!=NULL)
{
cout<<" "<<temp->data;
preorder(temp->left);
preorder(temp->right);
}
}
void inorder(struct st *temp)
{
if(temp!=NULL)
{
inorder(temp->left);
cout<<" "<<temp->data;
inorder(temp->right);

}
}
void postorder(struct st *temp)
{
if(temp!=NULL)
{
postorder(temp->left);
postorder(temp->right);
cout<<" "<<temp->data;
}
}
```

Output:

``` 1.insert Elements
2.preorder
3.inorder
4.postorder
5.exit

enter the value 5

1.insert Elements
2.preorder
3.inorder
4.postorder
5.exit

enter the value 1

1.insert Elements
2.preorder
3.inorder
4.postorder
5.exit

enter the value 3

1.insert Elements
2.preorder
3.inorder
4.postorder
5.exit

enter the value 2

1.insert Elements
2.preorder
3.inorder
4.postorder
5.exit

enter the value 4

1.insert Elements
2.preorder
3.inorder
4.postorder
5.exit
5 1 3 2 4
1.insert Elements
2.preorder
3.inorder
4.postorder
5.exit
1 2 3 4 5
1.insert Elements
2.preorder
3.inorder
4.postorder
5.exit