# Sudo Placement[1.4] | BST Traversal

Given N elements to be inserted into Binary Search Tree. The task is to construct a binary search tree with only insert operation and finally print the elements in the postorder traversal. The BST is constructed according to the arrival order of elements.

Examples:

```Input: N elements =  {8, 5, 10, 3, 4, 9, 7}
Output: 4 3 7 5 9 10 8

For the above input, the BST is:
8
/    \
5         10
/   \      /
3     7    9
\
4
The post-order traversal of the above BST is 4 3 7 5 9 10 8
```

## Recommended: Please try your approach on {IDE} first, before moving on to the solution.

Approach: The approach to solve this problem is to construct the BST using insertion method in BST. Once all the nodes are inserted, print the postorder traversal of the tree.

Below is the implementation of the above approach:

## C++

 `// C++ program to insert nodes ` `// and print the postorder traversal ` `#include ` `using` `namespace` `std; ` ` `  `// structure to store the BST ` `struct` `Node { ` `    ``int` `data; ` `    ``Node* left = NULL; ` `    ``Node* right = NULL; ` `}; ` ` `  `// locates the memory space ` `Node* newNode(``int` `key) ` `{ ` `    ``Node* temp = ``new` `Node; ` `    ``temp->data = key; ` `    ``temp->left = NULL; ` `    ``temp->right = NULL; ` `    ``return` `temp; ` `} ` ` `  `// inserts node in the BST ` `Node* insertNode(Node* head, ``int` `key) ` `{ ` `    ``// if first node ` `    ``if` `(head == NULL) ` `        ``head = newNode(key); ` `    ``else` `{ ` `        ``// move to left ` `        ``if` `(key < head->data) ` `            ``head->left = insertNode(head->left, key); ` `        ``// move to right ` `        ``else` `            ``head->right = insertNode(head->right, key); ` `    ``} ` `    ``return` `head; ` `} ` ` `  `// print the postorder traversal ` `void` `posOrder(Node* head) ` `{ ` `    ``// leaf node is null ` `    ``if` `(head == NULL) ` `        ``return``; ` ` `  `    ``// left ` `    ``posOrder(head->left); ` ` `  `    ``// right ` `    ``posOrder(head->right); ` ` `  `    ``// data ` `    ``cout << head->data << ``" "``; ` `} ` ` `  `// Driver Code ` `int` `main() ` `{ ` ` `  `    ``Node* root = NULL; ` `    ``root = insertNode(root, 8); ` `    ``root = insertNode(root, 5); ` `    ``root = insertNode(root, 10); ` `    ``root = insertNode(root, 3); ` `    ``root = insertNode(root, 4); ` `    ``root = insertNode(root, 9); ` `    ``root = insertNode(root, 7); ` ` `  `    ``// prints the postorder traversal of ` `    ``// the tree ` `    ``posOrder(root); ` `    ``cout << endl; ` `} `

## Java

 `// Java program to insert nodes ` `// and print the postorder traversal ` `class` `GFG { ` ` `  `    ``// structure to store the BST ` `    ``static` `class` `Node { ` `        ``int` `data; ` `        ``Node left = ``null``; ` `        ``Node right = ``null``; ` `    ``}; ` ` `  `    ``// locates the memory space ` `    ``static` `Node newNode(``int` `key) ` `    ``{ ` `        ``Node temp = ``new` `Node(); ` `        ``temp.data = key; ` `        ``temp.left = ``null``; ` `        ``temp.right = ``null``; ` `        ``return` `temp; ` `    ``} ` ` `  `    ``// inserts node in the BST ` `    ``static` `Node insertNode(Node head, ``int` `key) ` `    ``{ ` `        ``// if first node ` `        ``if` `(head == ``null``) ` `            ``head = newNode(key); ` `        ``else` `{ ` `            ``// move to left ` `            ``if` `(key < head.data) ` `                ``head.left = insertNode(head.left, key); ` `            ``// move to right ` `            ``else` `                ``head.right = insertNode(head.right, key); ` `        ``} ` `        ``return` `head; ` `    ``} ` ` `  `    ``// print the postorder traversal ` `    ``static` `void` `posOrder(Node head) ` `    ``{ ` `        ``// leaf node is null ` `        ``if` `(head == ``null``) ` `            ``return``; ` ` `  `        ``// left ` `        ``posOrder(head.left); ` ` `  `        ``// right ` `        ``posOrder(head.right); ` ` `  `        ``// data ` `        ``System.out.print(head.data + ``" "``); ` `    ``} ` ` `  `    ``// Driver Code ` `    ``public` `static` `void` `main(String[] args) ` `    ``{ ` `        ``Node root = ``new` `Node(); ` `        ``root = insertNode(root, ``8``); ` `        ``root = insertNode(root, ``5``); ` `        ``root = insertNode(root, ``10``); ` `        ``root = insertNode(root, ``3``); ` `        ``root = insertNode(root, ``4``); ` `        ``root = insertNode(root, ``9``); ` `        ``root = insertNode(root, ``7``); ` ` `  `        ``// prints the postorder traversal of ` `        ``// the tree ` `        ``posOrder(root); ` `        ``System.out.println(``""``); ` `    ``} ` `} ` ` `  `// This code has been contributed by 29AjayKumar `

## Python3

 `# Python program to insert nodes ` `# and print the postorder traversal ` `import` `math ` ` `  `# structure to store the BST ` `class` `Node:  ` `    ``def` `__init__(``self``,data):  ` `        ``self``.data ``=` `data  ` `        ``self``.left ``=` `None` `        ``self``.right``=``None` ` `  `# locates the memory space ` `def` `newNode(key): ` `    ``temp ``=` `Node(key) ` `    ``temp.data ``=` `key ` `    ``temp.left ``=` `None` `    ``temp.right ``=` `None` `    ``return` `temp ` ` `  `# inserts node in the BST ` `def` `insertNode(head, key): ` `     `  `    ``# if first node ` `    ``if` `(head ``=``=` `None``): ` `        ``head ``=` `newNode(key) ` `    ``else` `: ` `         `  `        ``# move to left ` `        ``if` `(key < head.data): ` `            ``head.left ``=` `insertNode(head.left, key) ` `         `  `        ``# move to right ` `        ``else``: ` `            ``head.right ``=` `insertNode(head.right, key) ` `     `  `    ``return` `head ` ` `  `# print the postorder traversal ` `def` `posOrder(head): ` `     `  `    ``# leaf node is None ` `    ``if` `(head ``=``=` `None``): ` `        ``return` ` `  `    ``# left ` `    ``posOrder(head.left) ` ` `  `    ``# right ` `    ``posOrder(head.right) ` ` `  `    ``# data ` `    ``print``(head.data,end ``=` `" "``) ` ` `  `# Driver Code ` `if` `__name__``=``=``'__main__'``:  ` `    ``root ``=` `None` `    ``root ``=` `insertNode(root, ``8``) ` `    ``root ``=` `insertNode(root, ``5``) ` `    ``root ``=` `insertNode(root, ``10``) ` `    ``root ``=` `insertNode(root, ``3``) ` `    ``root ``=` `insertNode(root, ``4``) ` `    ``root ``=` `insertNode(root, ``9``) ` `    ``root ``=` `insertNode(root, ``7``) ` ` `  `    ``# prints the postorder traversal of ` `    ``# the tree ` `    ``posOrder(root) ` ` `  `# This code is contributed by Srathore `

## C#

 `// C# program to insert nodes ` `// and print the postorder traversal ` `using` `System; ` ` `  `class` `GFG { ` ` `  `    ``// structure to store the BST ` `    ``public` `class` `Node { ` `        ``public` `int` `data; ` `        ``public` `Node left = ``null``; ` `        ``public` `Node right = ``null``; ` `    ``}; ` ` `  `    ``// locates the memory space ` `    ``static` `Node newNode(``int` `key) ` `    ``{ ` `        ``Node temp = ``new` `Node(); ` `        ``temp.data = key; ` `        ``temp.left = ``null``; ` `        ``temp.right = ``null``; ` `        ``return` `temp; ` `    ``} ` ` `  `    ``// inserts node in the BST ` `    ``static` `Node insertNode(Node head, ``int` `key) ` `    ``{ ` `        ``// if first node ` `        ``if` `(head == ``null``) ` `            ``head = newNode(key); ` `        ``else` `{ ` `            ``// move to left ` `            ``if` `(key < head.data) ` `                ``head.left = insertNode(head.left, key); ` `            ``// move to right ` `            ``else` `                ``head.right = insertNode(head.right, key); ` `        ``} ` `        ``return` `head; ` `    ``} ` ` `  `    ``// print the postorder traversal ` `    ``static` `void` `posOrder(Node head) ` `    ``{ ` `        ``// leaf node is null ` `        ``if` `(head == ``null``) ` `            ``return``; ` ` `  `        ``// left ` `        ``posOrder(head.left); ` ` `  `        ``// right ` `        ``posOrder(head.right); ` ` `  `        ``// data ` `        ``Console.Write(head.data + ``" "``); ` `    ``} ` ` `  `    ``// Driver Code ` `    ``public` `static` `void` `Main(String[] args) ` `    ``{ ` `        ``Node root = ``new` `Node(); ` `        ``root = insertNode(root, 8); ` `        ``root = insertNode(root, 5); ` `        ``root = insertNode(root, 10); ` `        ``root = insertNode(root, 3); ` `        ``root = insertNode(root, 4); ` `        ``root = insertNode(root, 9); ` `        ``root = insertNode(root, 7); ` ` `  `        ``// prints the postorder traversal of ` `        ``// the tree ` `        ``posOrder(root); ` `        ``Console.WriteLine(``""``); ` `    ``} ` `} ` ` `  `// This code contributed by Rajput-Ji `

Output:

`4 3 7 5 9 10 8`

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