# Binary Search Tree | Set 2 (Delete)

We have discussed BST search and insert operations. In this post, delete operation is discussed. When we delete a node, three possibilities arise.
1) Node to be deleted is leaf: Simply remove from the tree.

```              50                            50
/     \         delete(20)      /   \
30      70       --------->    30     70
/  \    /  \                     \    /  \
20   40  60   80                   40  60   80```

2) Node to be deleted has only one child: Copy the child to the node and delete the child

```              50                            50
/     \         delete(30)      /   \
30      70       --------->    40     70
\    /  \                          /  \
40  60   80                       60   80```

3) Node to be deleted has two children: Find inorder successor of the node. Copy contents of the inorder successor to the node and delete the inorder successor. Note that inorder predecessor can also be used.

```              50                            60
/     \         delete(50)      /   \
40      70       --------->    40    70
/  \                            \
60   80                           80```

The important thing to note is, inorder successor is needed only when right child is not empty. In this particular case, inorder successor can be obtained by finding the minimum value in right child of the node.

## C/C++

 `// C program to demonstrate delete operation in binary search tree ` `#include ` `#include ` ` `  `struct` `node ` `{ ` `    ``int` `key; ` `    ``struct` `node *left, *right; ` `}; ` ` `  `// A utility function to create a new BST node ` `struct` `node *newNode(``int` `item) ` `{ ` `    ``struct` `node *temp =  (``struct` `node *)``malloc``(``sizeof``(``struct` `node)); ` `    ``temp->key = item; ` `    ``temp->left = temp->right = NULL; ` `    ``return` `temp; ` `} ` ` `  `// A utility function to do inorder traversal of BST ` `void` `inorder(``struct` `node *root) ` `{ ` `    ``if` `(root != NULL) ` `    ``{ ` `        ``inorder(root->left); ` `        ``printf``(``"%d "``, root->key); ` `        ``inorder(root->right); ` `    ``} ` `} ` ` `  `/* A utility function to insert a new node with given key in BST */` `struct` `node* insert(``struct` `node* node, ``int` `key) ` `{ ` `    ``/* If the tree is empty, return a new node */` `    ``if` `(node == NULL) ``return` `newNode(key); ` ` `  `    ``/* Otherwise, recur down the tree */` `    ``if` `(key < node->key) ` `        ``node->left  = insert(node->left, key); ` `    ``else` `        ``node->right = insert(node->right, key); ` ` `  `    ``/* return the (unchanged) node pointer */` `    ``return` `node; ` `} ` ` `  `/* Given a non-empty binary search tree, return the node with minimum ` `   ``key value found in that tree. Note that the entire tree does not ` `   ``need to be searched. */` `struct` `node * minValueNode(``struct` `node* node) ` `{ ` `    ``struct` `node* current = node; ` ` `  `    ``/* loop down to find the leftmost leaf */` `    ``while` `(current && current->left != NULL) ` `        ``current = current->left; ` ` `  `    ``return` `current; ` `} ` ` `  `/* Given a binary search tree and a key, this function deletes the key ` `   ``and returns the new root */` `struct` `node* deleteNode(``struct` `node* root, ``int` `key) ` `{ ` `    ``// base case ` `    ``if` `(root == NULL) ``return` `root; ` ` `  `    ``// If the key to be deleted is smaller than the root's key, ` `    ``// then it lies in left subtree ` `    ``if` `(key < root->key) ` `        ``root->left = deleteNode(root->left, key); ` ` `  `    ``// If the key to be deleted is greater than the root's key, ` `    ``// then it lies in right subtree ` `    ``else` `if` `(key > root->key) ` `        ``root->right = deleteNode(root->right, key); ` ` `  `    ``// if key is same as root's key, then This is the node ` `    ``// to be deleted ` `    ``else` `    ``{ ` `        ``// node with only one child or no child ` `        ``if` `(root->left == NULL) ` `        ``{ ` `            ``struct` `node *temp = root->right; ` `            ``free``(root); ` `            ``return` `temp; ` `        ``} ` `        ``else` `if` `(root->right == NULL) ` `        ``{ ` `            ``struct` `node *temp = root->left; ` `            ``free``(root); ` `            ``return` `temp; ` `        ``} ` ` `  `        ``// node with two children: Get the inorder successor (smallest ` `        ``// in the right subtree) ` `        ``struct` `node* temp = minValueNode(root->right); ` ` `  `        ``// Copy the inorder successor's content to this node ` `        ``root->key = temp->key; ` ` `  `        ``// Delete the inorder successor ` `        ``root->right = deleteNode(root->right, temp->key); ` `    ``} ` `    ``return` `root; ` `} ` ` `  `// Driver Program to test above functions ` `int` `main() ` `{ ` `    ``/* Let us create following BST ` `              ``50 ` `           ``/     \ ` `          ``30      70 ` `         ``/  \    /  \ ` `       ``20   40  60   80 */` `    ``struct` `node *root = NULL; ` `    ``root = insert(root, 50); ` `    ``root = insert(root, 30); ` `    ``root = insert(root, 20); ` `    ``root = insert(root, 40); ` `    ``root = insert(root, 70); ` `    ``root = insert(root, 60); ` `    ``root = insert(root, 80); ` ` `  `    ``printf``(``"Inorder traversal of the given tree \n"``); ` `    ``inorder(root); ` ` `  `    ``printf``(``"\nDelete 20\n"``); ` `    ``root = deleteNode(root, 20); ` `    ``printf``(``"Inorder traversal of the modified tree \n"``); ` `    ``inorder(root); ` ` `  `    ``printf``(``"\nDelete 30\n"``); ` `    ``root = deleteNode(root, 30); ` `    ``printf``(``"Inorder traversal of the modified tree \n"``); ` `    ``inorder(root); ` ` `  `    ``printf``(``"\nDelete 50\n"``); ` `    ``root = deleteNode(root, 50); ` `    ``printf``(``"Inorder traversal of the modified tree \n"``); ` `    ``inorder(root); ` ` `  `    ``return` `0; ` `} `

## Java

 `// Java program to demonstrate delete operation in binary search tree ` `class` `BinarySearchTree ` `{ ` `    ``/* Class containing left and right child of current node and key value*/` `    ``class` `Node ` `    ``{ ` `        ``int` `key; ` `        ``Node left, right; ` ` `  `        ``public` `Node(``int` `item) ` `        ``{ ` `            ``key = item; ` `            ``left = right = ``null``; ` `        ``} ` `    ``} ` ` `  `    ``// Root of BST ` `    ``Node root; ` ` `  `    ``// Constructor ` `    ``BinarySearchTree() ` `    ``{ ` `        ``root = ``null``; ` `    ``} ` ` `  `    ``// This method mainly calls deleteRec() ` `    ``void` `deleteKey(``int` `key) ` `    ``{ ` `        ``root = deleteRec(root, key); ` `    ``} ` ` `  `    ``/* A recursive function to insert a new key in BST */` `    ``Node deleteRec(Node root, ``int` `key) ` `    ``{ ` `        ``/* Base Case: If the tree is empty */` `        ``if` `(root == ``null``)  ``return` `root; ` ` `  `        ``/* Otherwise, recur down the tree */` `        ``if` `(key < root.key) ` `            ``root.left = deleteRec(root.left, key); ` `        ``else` `if` `(key > root.key) ` `            ``root.right = deleteRec(root.right, key); ` ` `  `        ``// if key is same as root's key, then This is the node ` `        ``// to be deleted ` `        ``else` `        ``{ ` `            ``// node with only one child or no child ` `            ``if` `(root.left == ``null``) ` `                ``return` `root.right; ` `            ``else` `if` `(root.right == ``null``) ` `                ``return` `root.left; ` ` `  `            ``// node with two children: Get the inorder successor (smallest ` `            ``// in the right subtree) ` `            ``root.key = minValue(root.right); ` ` `  `            ``// Delete the inorder successor ` `            ``root.right = deleteRec(root.right, root.key); ` `        ``} ` ` `  `        ``return` `root; ` `    ``} ` ` `  `    ``int` `minValue(Node root) ` `    ``{ ` `        ``int` `minv = root.key; ` `        ``while` `(root.left != ``null``) ` `        ``{ ` `            ``minv = root.left.key; ` `            ``root = root.left; ` `        ``} ` `        ``return` `minv; ` `    ``} ` ` `  `    ``// This method mainly calls insertRec() ` `    ``void` `insert(``int` `key) ` `    ``{ ` `        ``root = insertRec(root, key); ` `    ``} ` ` `  `    ``/* A recursive function to insert a new key in BST */` `    ``Node insertRec(Node root, ``int` `key) ` `    ``{ ` ` `  `        ``/* If the tree is empty, return a new node */` `        ``if` `(root == ``null``) ` `        ``{ ` `            ``root = ``new` `Node(key); ` `            ``return` `root; ` `        ``} ` ` `  `        ``/* Otherwise, recur down the tree */` `        ``if` `(key < root.key) ` `            ``root.left = insertRec(root.left, key); ` `        ``else` `if` `(key > root.key) ` `            ``root.right = insertRec(root.right, key); ` ` `  `        ``/* return the (unchanged) node pointer */` `        ``return` `root; ` `    ``} ` ` `  `    ``// This method mainly calls InorderRec() ` `    ``void` `inorder() ` `    ``{ ` `        ``inorderRec(root); ` `    ``} ` ` `  `    ``// A utility function to do inorder traversal of BST ` `    ``void` `inorderRec(Node root) ` `    ``{ ` `        ``if` `(root != ``null``) ` `        ``{ ` `            ``inorderRec(root.left); ` `            ``System.out.print(root.key + ``" "``); ` `            ``inorderRec(root.right); ` `        ``} ` `    ``} ` ` `  `    ``// Driver Program to test above functions ` `    ``public` `static` `void` `main(String[] args) ` `    ``{ ` `        ``BinarySearchTree tree = ``new` `BinarySearchTree(); ` ` `  `        ``/* Let us create following BST ` `              ``50 ` `           ``/     \ ` `          ``30      70 ` `         ``/  \    /  \ ` `        ``20   40  60   80 */` `        ``tree.insert(``50``); ` `        ``tree.insert(``30``); ` `        ``tree.insert(``20``); ` `        ``tree.insert(``40``); ` `        ``tree.insert(``70``); ` `        ``tree.insert(``60``); ` `        ``tree.insert(``80``); ` ` `  `        ``System.out.println(``"Inorder traversal of the given tree"``); ` `        ``tree.inorder(); ` ` `  `        ``System.out.println(``"\nDelete 20"``); ` `        ``tree.deleteKey(``20``); ` `        ``System.out.println(``"Inorder traversal of the modified tree"``); ` `        ``tree.inorder(); ` ` `  `        ``System.out.println(``"\nDelete 30"``); ` `        ``tree.deleteKey(``30``); ` `        ``System.out.println(``"Inorder traversal of the modified tree"``); ` `        ``tree.inorder(); ` ` `  `        ``System.out.println(``"\nDelete 50"``); ` `        ``tree.deleteKey(``50``); ` `        ``System.out.println(``"Inorder traversal of the modified tree"``); ` `        ``tree.inorder(); ` `    ``} ` `} `

## Python

 `# Python program to demonstrate delete operation ` `# in binary search tree ` ` `  `# A Binary Tree Node ` `class` `Node: ` ` `  `    ``# Constructor to create a new node ` `    ``def` `__init__(``self``, key): ` `        ``self``.key ``=` `key  ` `        ``self``.left ``=` `None` `        ``self``.right ``=` `None` ` `  ` `  `# A utility function to do inorder traversal of BST ` `def` `inorder(root): ` `    ``if` `root ``is` `not` `None``: ` `        ``inorder(root.left) ` `        ``print` `root.key, ` `        ``inorder(root.right) ` ` `  ` `  `# A utility function to insert a new node with given key in BST ` `def` `insert( node, key): ` ` `  `    ``# If the tree is empty, return a new node ` `    ``if` `node ``is` `None``: ` `        ``return` `Node(key) ` ` `  `    ``# Otherwise recur down the tree ` `    ``if` `key < node.key: ` `        ``node.left ``=` `insert(node.left, key) ` `    ``else``: ` `        ``node.right ``=` `insert(node.right, key) ` ` `  `    ``# return the (unchanged) node pointer ` `    ``return` `node ` ` `  `# Given a non-empty binary search tree, return the node ` `# with minum key value found in that tree. Note that the ` `# entire tree does not need to be searched  ` `def` `minValueNode( node): ` `    ``current ``=` `node ` ` `  `    ``# loop down to find the leftmost leaf ` `    ``while``(current.left ``is` `not` `None``): ` `        ``current ``=` `current.left  ` ` `  `    ``return` `current  ` ` `  `# Given a binary search tree and a key, this function ` `# delete the key and returns the new root ` `def` `deleteNode(root, key): ` ` `  `    ``# Base Case ` `    ``if` `root ``is` `None``: ` `        ``return` `root  ` ` `  `    ``# If the key to be deleted is smaller than the root's ` `    ``# key then it lies in  left subtree ` `    ``if` `key < root.key: ` `        ``root.left ``=` `deleteNode(root.left, key) ` ` `  `    ``# If the kye to be delete is greater than the root's key ` `    ``# then it lies in right subtree ` `    ``elif``(key > root.key): ` `        ``root.right ``=` `deleteNode(root.right, key) ` ` `  `    ``# If key is same as root's key, then this is the node ` `    ``# to be deleted ` `    ``else``: ` `         `  `        ``# Node with only one child or no child ` `        ``if` `root.left ``is` `None` `: ` `            ``temp ``=` `root.right  ` `            ``root ``=` `None`  `            ``return` `temp  ` `             `  `        ``elif` `root.right ``is` `None` `: ` `            ``temp ``=` `root.left  ` `            ``root ``=` `None` `            ``return` `temp ` ` `  `        ``# Node with two children: Get the inorder successor ` `        ``# (smallest in the right subtree) ` `        ``temp ``=` `minValueNode(root.right) ` ` `  `        ``# Copy the inorder successor's content to this node ` `        ``root.key ``=` `temp.key ` ` `  `        ``# Delete the inorder successor ` `        ``root.right ``=` `deleteNode(root.right , temp.key) ` ` `  ` `  `    ``return` `root  ` ` `  `# Driver program to test above functions ` `""" Let us create following BST ` `              ``50 ` `           ``/     \ ` `          ``30      70 ` `         ``/  \    /  \ ` `       ``20   40  60   80 """` ` `  `root ``=` `None` `root ``=` `insert(root, ``50``) ` `root ``=` `insert(root, ``30``) ` `root ``=` `insert(root, ``20``) ` `root ``=` `insert(root, ``40``) ` `root ``=` `insert(root, ``70``) ` `root ``=` `insert(root, ``60``) ` `root ``=` `insert(root, ``80``) ` ` `  `print` `"Inorder traversal of the given tree"` `inorder(root) ` ` `  `print` `"\nDelete 20"` `root ``=` `deleteNode(root, ``20``) ` `print` `"Inorder traversal of the modified tree"` `inorder(root) ` ` `  `print` `"\nDelete 30"` `root ``=` `deleteNode(root, ``30``) ` `print` `"Inorder traversal of the modified tree"` `inorder(root) ` ` `  `print` `"\nDelete 50"` `root ``=` `deleteNode(root, ``50``) ` `print` `"Inorder traversal of the modified tree"` `inorder(root) ` ` `  `# This code is contributed by Nikhil Kumar Singh(nickzuck_007) `

## C#

 `// C# program to demonstrate delete  ` `// operation in binary search tree ` `using` `System; ` ` `  `public` `class` `BinarySearchTree  ` `{  ` `    ``/* Class containing left and right  ` `    ``child of current node and key value*/` `    ``class` `Node  ` `    ``{  ` `        ``public` `int` `key;  ` `        ``public` `Node left, right;  ` ` `  `        ``public` `Node(``int` `item)  ` `        ``{  ` `            ``key = item;  ` `            ``left = right = ``null``;  ` `        ``}  ` `    ``}  ` ` `  `    ``// Root of BST  ` `    ``Node root;  ` ` `  `    ``// Constructor  ` `    ``BinarySearchTree()  ` `    ``{  ` `        ``root = ``null``;  ` `    ``}  ` ` `  `    ``// This method mainly calls deleteRec()  ` `    ``void` `deleteKey(``int` `key)  ` `    ``{  ` `        ``root = deleteRec(root, key);  ` `    ``}  ` ` `  `    ``/* A recursive function to insert a new key in BST */` `    ``Node deleteRec(Node root, ``int` `key)  ` `    ``{  ` `        ``/* Base Case: If the tree is empty */` `        ``if` `(root == ``null``) ``return` `root;  ` ` `  `        ``/* Otherwise, recur down the tree */` `        ``if` `(key < root.key)  ` `            ``root.left = deleteRec(root.left, key);  ` `        ``else` `if` `(key > root.key)  ` `            ``root.right = deleteRec(root.right, key);  ` ` `  `        ``// if key is same as root's key, then This is the node  ` `        ``// to be deleted  ` `        ``else` `        ``{  ` `            ``// node with only one child or no child  ` `            ``if` `(root.left == ``null``)  ` `                ``return` `root.right;  ` `            ``else` `if` `(root.right == ``null``)  ` `                ``return` `root.left;  ` ` `  `            ``// node with two children: Get the ` `            ``// inorder successor (smallest  ` `            ``// in the right subtree)  ` `            ``root.key = minValue(root.right);  ` ` `  `            ``// Delete the inorder successor  ` `            ``root.right = deleteRec(root.right, root.key);  ` `        ``}  ` `        ``return` `root;  ` `    ``}  ` ` `  `    ``int` `minValue(Node root)  ` `    ``{  ` `        ``int` `minv = root.key;  ` `        ``while` `(root.left != ``null``)  ` `        ``{  ` `            ``minv = root.left.key;  ` `            ``root = root.left;  ` `        ``}  ` `        ``return` `minv;  ` `    ``}  ` ` `  `    ``// This method mainly calls insertRec()  ` `    ``void` `insert(``int` `key)  ` `    ``{  ` `        ``root = insertRec(root, key);  ` `    ``}  ` ` `  `    ``/* A recursive function to insert a new key in BST */` `    ``Node insertRec(Node root, ``int` `key)  ` `    ``{  ` ` `  `        ``/* If the tree is empty, return a new node */` `        ``if` `(root == ``null``)  ` `        ``{  ` `            ``root = ``new` `Node(key);  ` `            ``return` `root;  ` `        ``}  ` ` `  `        ``/* Otherwise, recur down the tree */` `        ``if` `(key < root.key)  ` `            ``root.left = insertRec(root.left, key);  ` `        ``else` `if` `(key > root.key)  ` `            ``root.right = insertRec(root.right, key);  ` ` `  `        ``/* return the (unchanged) node pointer */` `        ``return` `root;  ` `    ``}  ` ` `  `    ``// This method mainly calls InorderRec()  ` `    ``void` `inorder()  ` `    ``{  ` `        ``inorderRec(root);  ` `    ``}  ` ` `  `    ``// A utility function to do inorder traversal of BST  ` `    ``void` `inorderRec(Node root)  ` `    ``{  ` `        ``if` `(root != ``null``)  ` `        ``{  ` `            ``inorderRec(root.left);  ` `            ``Console.Write(root.key + ``" "``);  ` `            ``inorderRec(root.right);  ` `        ``}  ` `    ``}  ` ` `  `    ``// Driver code  ` `    ``public` `static` `void` `Main(String[] args)  ` `    ``{  ` `        ``BinarySearchTree tree = ``new` `BinarySearchTree();  ` ` `  `        ``/* Let us create following BST  ` `            ``50  ` `        ``/ \  ` `        ``30 70  ` `        ``/ \ / \  ` `        ``20 40 60 80 */` `        ``tree.insert(50);  ` `        ``tree.insert(30);  ` `        ``tree.insert(20);  ` `        ``tree.insert(40);  ` `        ``tree.insert(70);  ` `        ``tree.insert(60);  ` `        ``tree.insert(80);  ` ` `  `        ``Console.WriteLine(``"Inorder traversal of the given tree"``);  ` `        ``tree.inorder();  ` ` `  `        ``Console.WriteLine(``"\nDelete 20"``);  ` `        ``tree.deleteKey(20);  ` `        ``Console.WriteLine(``"Inorder traversal of the modified tree"``);  ` `        ``tree.inorder();  ` ` `  `        ``Console.WriteLine(``"\nDelete 30"``);  ` `        ``tree.deleteKey(30);  ` `        ``Console.WriteLine(``"Inorder traversal of the modified tree"``);  ` `        ``tree.inorder();  ` ` `  `        ``Console.WriteLine(``"\nDelete 50"``);  ` `        ``tree.deleteKey(50);  ` `        ``Console.WriteLine(``"Inorder traversal of the modified tree"``);  ` `        ``tree.inorder();  ` `    ``}  ` `}  ` ` `  `// This code has been contributed  ` `// by PrinciRaj1992 `

Output:

```Inorder traversal of the given tree
20 30 40 50 60 70 80
Delete 20
Inorder traversal of the modified tree
30 40 50 60 70 80
Delete 30
Inorder traversal of the modified tree
40 50 60 70 80
Delete 50
Inorder traversal of the modified tree
40 60 70 80
```

Illustration:  Time Complexity: The worst case time complexity of delete operation is O(h) where h is height of Binary Search Tree. In worst case, we may have to travel from root to the deepest leaf node. The height of a skewed tree may become n and the time complexity of delete operation may become O(n)

Optimization to above code for two children case :
In the above recursive code, we recursively call delete() for successor. We can avoid recursive call by keeping track of parent node of successor so that we can simply remove the successor by making child of parent as NULL. We know that successor would always be a leaf node.

 `// C++ program to implement optimized delete in BST. ` `#include ` `using` `namespace` `std; ` ` `  `struct` `Node { ` `    ``int` `key; ` `    ``struct` `Node *left, *right; ` `}; ` ` `  `// A utility function to create a new BST node ` `Node* newNode(``int` `item) ` `{ ` `    ``Node* temp = ``new` `Node; ` `    ``temp->key = item; ` `    ``temp->left = temp->right = NULL; ` `    ``return` `temp; ` `} ` ` `  `// A utility function to do inorder traversal of BST ` `void` `inorder(Node* root) ` `{ ` `    ``if` `(root != NULL) { ` `        ``inorder(root->left); ` `        ``printf``(``"%d "``, root->key); ` `        ``inorder(root->right); ` `    ``} ` `} ` ` `  `/* A utility function to insert a new node with given key in BST */` `Node* insert(Node* node, ``int` `key) ` `{ ` `    ``/* If the tree is empty, return a new node */` `    ``if` `(node == NULL) ` `        ``return` `newNode(key); ` ` `  `    ``/* Otherwise, recur down the tree */` `    ``if` `(key < node->key) ` `        ``node->left = insert(node->left, key); ` `    ``else` `        ``node->right = insert(node->right, key); ` ` `  `    ``/* return the (unchanged) node pointer */` `    ``return` `node; ` `} ` ` `  `/* Given a binary search tree and a key, this function deletes the key ` `   ``and returns the new root */` `Node* deleteNode(Node* root, ``int` `k) ` `{ ` `    ``// Base case ` `    ``if` `(root == NULL) ` `        ``return` `root; ` ` `  `    ``// Recursive calls for ancestors of ` `    ``// node to be deleted ` `    ``if` `(root->key > k) { ` `        ``root->left = deleteNode(root->left, k); ` `        ``return` `root; ` `    ``} ` `    ``else` `if` `(root->key < k) { ` `        ``root->right = deleteNode(root->right, k); ` `        ``return` `root; ` `    ``} ` ` `  `    ``// We reach here when root is the node ` `    ``// to be deleted. ` ` `  `    ``// If one of the children is empty ` `    ``if` `(root->left == NULL) { ` `        ``Node* temp = root->right; ` `        ``delete` `root; ` `        ``return` `temp; ` `    ``} ` `    ``else` `if` `(root->right == NULL) { ` `        ``Node* temp = root->left; ` `        ``delete` `root; ` `        ``return` `temp; ` `    ``} ` ` `  `    ``// If both children exist ` `    ``else` `{ ` ` `  `        ``Node* succParent = root->right; ` `         `  `        ``// Find successor ` `        ``Node *succ = root->right; ` `        ``while` `(succ->left != NULL) { ` `            ``succParent = succ; ` `            ``succ = succ->left; ` `        ``} ` ` `  `        ``// Delete successor.  Since successor ` `        ``// is always left child of its parent ` `        ``// we can safely make successor's right ` `        ``// right child as left of its parent. ` `        ``succParent->left = succ->right; ` ` `  `        ``// Copy Successor Data to root ` `        ``root->key = succ->key; ` ` `  `        ``// Delete Successor and return root ` `        ``delete` `succ;          ` `        ``return` `root; ` `    ``} ` `} ` ` `  `// Driver Program to test above functions ` `int` `main() ` `{ ` `    ``/* Let us create following BST ` `              ``50 ` `           ``/     \ ` `          ``30      70 ` `         ``/  \    /  \ ` `       ``20   40  60   80 */` `    ``Node* root = NULL; ` `    ``root = insert(root, 50); ` `    ``root = insert(root, 30); ` `    ``root = insert(root, 20); ` `    ``root = insert(root, 40); ` `    ``root = insert(root, 70); ` `    ``root = insert(root, 60); ` `    ``root = insert(root, 80); ` ` `  `    ``printf``(``"Inorder traversal of the given tree \n"``); ` `    ``inorder(root); ` ` `  `    ``printf``(``"\nDelete 20\n"``); ` `    ``root = deleteNode(root, 20); ` `    ``printf``(``"Inorder traversal of the modified tree \n"``); ` `    ``inorder(root); ` ` `  `    ``printf``(``"\nDelete 30\n"``); ` `    ``root = deleteNode(root, 30); ` `    ``printf``(``"Inorder traversal of the modified tree \n"``); ` `    ``inorder(root); ` ` `  `    ``printf``(``"\nDelete 50\n"``); ` `    ``root = deleteNode(root, 50); ` `    ``printf``(``"Inorder traversal of the modified tree \n"``); ` `    ``inorder(root); ` ` `  `    ``return` `0; ` `} `

Output:

```Inorder traversal of the given tree
20 30 40 50 60 70 80
Delete 20
Inorder traversal of the modified tree
30 40 50 60 70 80
Delete 30
Inorder traversal of the modified tree
40 50 60 70 80
Delete 50
Inorder traversal of the modified tree
40 60 70 80
```

Thanks to wolffgang010 for suggesting above optimization.