# Delete leaf nodes with value k

Given a binary tree and value k. delete all the leaf nodes with value equal to k. If a node becomes leaf after deletion, then it should be deleted if it has value k.
Examples:

```Input :     4
/     \
5       5
/  \    /
3    1  5

Output :    4
/
5
/  \
3    1

```

1. Use PostOrder traversal.
2. When we encounter leaf nodes, then we check whether it is leaf node or not.
3. If it is leaf node and value equal to k, then delete it.
4. Else, Recurse for other nodes.

## C++

 `// C++ program to delete leaf nodes with  ` `// value equal to k.  ` `#include ` `using` `namespace` `std; ` ` `  `struct` `Node  ` `{  ` `    ``int` `data;  ` `    ``struct` `Node *left, *right;  ` `};  ` ` `  `struct` `Node* newNode(``int` `data)  ` `{  ` `    ``struct` `Node* newNode = ``new` `Node;  ` `    ``newNode->data = data;  ` `    ``newNode->left = newNode->right = NULL;  ` `    ``return` `(newNode);  ` `}  ` ` `  `// Function to delete leaf Node with value  ` `// equal to k  ` `Node* LeafNodesWithValueK(Node* root, ``int` `k)  ` `{  ` `    ``if` `(root == NULL)  ` `        ``return` `nullptr; ` `         `  `    ``root->left = LeafNodesWithValueK(root->left, k);  ` `    ``root->right = LeafNodesWithValueK(root->right, k);  ` `     `  `    ``// If the node is leaf, and its  ` `        ``// value is equal to k  ` ` `  `    ``if` `(root->data == k &&  ` `        ``root->left == NULL &&  ` `        ``root->right == NULL) ` `    ``{  ` `        ``return` `nullptr;  ` `    ``}  ` `    ``return` `root;  ` `}  ` ` `  `void` `postOrder(Node* root)  ` `{  ` `    ``if` `(root == NULL)  ` `        ``return``;  ` `         `  `    ``cout << root->data << ``" "``;  ` `     `  `    ``postOrder(root->left);  ` `    ``postOrder(root->right);  ` `}  ` ` `  `// Driver code ` `int` `main() ` `{ ` `    ``struct` `Node* root = newNode(4);  ` `    ``root->left = newNode(5);  ` `    ``root->right = newNode(5);  ` `    ``root->left->left = newNode(3);  ` `    ``root->left->right = newNode(1);  ` `    ``root->right->right = newNode(5);  ` `     `  `    ``cout << ``"Nodes in postorder before deletion \n"``;  ` `    ``postOrder(root);  ` `    ``cout << ``"\n"``; ` `     `  `    ``int` `k = 5; ` `    ``LeafNodesWithValueK(root, k);  ` `    ``cout << ``"Nodes in post order after "`   `            ``"required deletion \n"``;  ` `    ``postOrder(root);  ` `    ``return` `0;  ` `} ` ` `  `// This code is contributed by Stream_Cipher `

## Java

 `// Java program to delete leaf nodes with ` `// value equal to k. ` ` `  `class` `Node { ` `    ``int` `data; ` `    ``Node left; ` `    ``Node right; ` ` `  `    ``public` `Node(``int` `data) ` `    ``{ ` `        ``this``.data = data; ` `        ``this``.left = ``null``; ` `        ``this``.right = ``null``; ` `    ``} ` `} ` ` `  `public` `class` `LeafNodesWithValueK { ` ` `  `    ``// Function to delete leaf Node with value  ` `    ``// equal to k ` `    ``static` `Node delLeafValueK(Node root, ``int` `k) ` `    ``{ ` `        ``if` `(root == ``null``) ` `            ``return` `null``; ` ` `  `        ``root.left = delLeafValueK(root.left, k); ` `        ``root.right = delLeafValueK(root.right, k); ` ` `  `        ``// If the node is leaf, and its  ` `        ``// value is equal to k ` `        ``if` `((root.left == ``null` `&& ` `             ``root.right == ``null``) &&  ` `             ``root.data == k) ` `            ``return` `null``; ` ` `  `        ``return` `root; ` `    ``} ` ` `  `    ``static` `void` `postOrder(Node root) ` `    ``{ ` `       ``if` `(root == ``null``) ` `          ``return``; ` `       ``System.out.print(root.data + ``" "``); ` `       ``postOrder(root.left);  ` `       ``postOrder(root.right); ` `    ``} ` ` `  `    ``// Driver Code ` `    ``public` `static` `void` `main(String[] args) ` `    ``{ ` `        ``Node root = ``new` `Node(``4``); ` `        ``root.left = ``new` `Node(``5``); ` `        ``root.right = ``new` `Node(``5``); ` `        ``root.left.left = ``new` `Node(``3``); ` `        ``root.left.right = ``new` `Node(``1``); ` `        ``root.right.left = ``new` `Node(``5``); ` ` `  `        ``System.out.println(``"Nodes in postorder before deletion"``); ` `        ``postOrder(root); ` `        ``System.out.println(); ` `        ``System.out.println(``"Nodes in post order after required deletion"``); ` `        ``int` `k = ``5``; ` `        ``delLeafValueK(root, k); ` `        ``postOrder(root); ` `        ``System.out.println(); ` `    ``} ` `} `

## C#

 `// C# program to delete leaf nodes with ` `// value equal to k. ` `using` `System; ` ` `  `public` `class` `Node  ` `{ ` `    ``public` `int` `data; ` `    ``public` `Node left; ` `    ``public` `Node right; ` ` `  `    ``public` `Node(``int` `data) ` `    ``{ ` `        ``this``.data = data; ` `        ``this``.left = ``null``; ` `        ``this``.right = ``null``; ` `    ``} ` `} ` ` `  `public` `class` `LeafNodesWithValueK  ` `{ ` ` `  `    ``// Function to delete leaf Node with value  ` `    ``// equal to k ` `    ``static` `Node delLeafValueK(Node root, ``int` `k) ` `    ``{ ` `        ``if` `(root == ``null``) ` `            ``return` `null``; ` ` `  `        ``root.left = delLeafValueK(root.left, k); ` `        ``root.right = delLeafValueK(root.right, k); ` ` `  `        ``// If the node is leaf, and its  ` `        ``// value is equal to k ` `        ``if` `((root.left == ``null` `&& ` `            ``root.right == ``null``) &&  ` `            ``root.data == k) ` `            ``return` `null``; ` ` `  `        ``return` `root; ` `    ``} ` ` `  `    ``static` `void` `postOrder(Node root) ` `    ``{ ` `        ``if` `(root == ``null``) ` `            ``return``; ` `        ``Console.Write(root.data + ``" "``); ` `        ``postOrder(root.left);  ` `        ``postOrder(root.right); ` `    ``} ` ` `  `    ``// Driver Code ` `    ``public` `static` `void` `Main(String[] args) ` `    ``{ ` `        ``Node root = ``new` `Node(4); ` `        ``root.left = ``new` `Node(5); ` `        ``root.right = ``new` `Node(5); ` `        ``root.left.left = ``new` `Node(3); ` `        ``root.left.right = ``new` `Node(1); ` `        ``root.right.left = ``new` `Node(5); ` ` `  `        ``Console.WriteLine(``"Nodes in postorder before deletion"``); ` `        ``postOrder(root); ` `        ``Console.WriteLine(); ` `        ``Console.WriteLine(``"Nodes in post order after required deletion"``); ` `        ``int` `k = 5; ` `        ``delLeafValueK(root, k); ` `        ``postOrder(root); ` `        ``Console.WriteLine(); ` `    ``} ` `} ` ` `  `// This code has been contributed by 29AjayKumar `

Output:

```Nodes in postorder before deletion
4 5 3 1 5 5
Nodes in post order after required deletion
4 5 3 1
```

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Improved By : 29AjayKumar, Stream_Cipher

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