# Maximum element between two nodes of BST

• Difficulty Level : Medium
• Last Updated : 30 Nov, 2022

Given an array of N elements and two integers A, B which belong to the given array. Create a Binary Search Tree by inserting elements from arr[0] to arr[n-1]. The task is to find the maximum element in the path from A to B.

Examples :

```Input : arr[] = { 18, 36, 9, 6, 12, 10, 1, 8 },
a = 1,
b = 10.

Output : 12
```

Path from 1 to 10 contains { 1, 6, 9, 12, 10 }. The maximum element is 12.

The idea is to find Lowest Common Ancestor of node ‘a’ and node ‘b’. Then search maximum node between LCA and ‘a’, and also find the maximum node between LCA and ‘b’. The answer will be maximum node of two.

Implementation:

## C++

 `// C++ program to find maximum element in the path``// between two Nodes of Binary Search Tree.``#include ``using` `namespace` `std;` `struct` `Node``{``    ``struct` `Node *left, *right;``    ``int` `data;``};` `// Create and return a pointer of new Node.``Node *createNode(``int` `x)``{``    ``Node *p = ``new` `Node;``    ``p -> data = x;``    ``p -> left = p -> right = NULL;``    ``return` `p;``}` `// Insert a new Node in Binary Search Tree.``void` `insertNode(``struct` `Node *root, ``int` `x)``{``    ``Node *p = root, *q = NULL;` `    ``while` `(p != NULL)``    ``{``        ``q = p;``        ``if` `(p -> data < x)``            ``p = p -> right;``        ``else``            ``p = p -> left;``    ``}` `    ``if` `(q == NULL)``        ``p = createNode(x);``    ``else``    ``{``        ``if` `(q -> data < x)``            ``q -> right = createNode(x);``        ``else``            ``q -> left = createNode(x);``    ``}``}` `// Return the maximum element between a Node``// and its given ancestor.``int` `maxelpath(Node *q, ``int` `x)``{``    ``Node *p = q;` `    ``int` `mx = INT_MIN;` `    ``// Traversing the path between ancestor and``    ``// Node and finding maximum element.``    ``while` `(p -> data != x)``    ``{``        ``if` `(p -> data > x)``        ``{``            ``mx = max(mx, p -> data);``            ``p = p -> left;``        ``}``        ``else``        ``{``            ``mx = max(mx, p -> data);``            ``p = p -> right;``        ``}``    ``}` `    ``return` `max(mx, x);``}` `// Return maximum element in the path between``// two given Node of BST.``int` `maximumElement(``struct` `Node *root, ``int` `x, ``int` `y)``{``    ``Node *p = root;` `    ``// Finding the LCA of Node x and Node y``    ``while` `((x < p -> data && y < p -> data) ||``        ``(x > p -> data && y > p -> data))``    ``{``        ``// Checking if both the Node lie on the``        ``// left side of the parent p.``        ``if` `(x < p -> data && y < p -> data)``            ``p = p -> left;` `        ``// Checking if both the Node lie on the``        ``// right side of the parent p.``        ``else` `if` `(x > p -> data && y > p -> data)``            ``p = p -> right;``    ``}` `    ``// Return the maximum of maximum elements occur``    ``// in path from ancestor to both Node.``    ``return` `max(maxelpath(p, x), maxelpath(p, y));``}`  `// Driver Code``int` `main()``{``    ``int` `arr[] = { 18, 36, 9, 6, 12, 10, 1, 8 };``    ``int` `a = 1, b = 10;``    ``int` `n = ``sizeof``(arr) / ``sizeof``(arr[0]);` `    ``// Creating the root of Binary Search Tree``    ``struct` `Node *root = createNode(arr[0]);` `    ``// Inserting Nodes in Binary Search Tree``    ``for` `(``int` `i = 1; i < n; i++)``        ``insertNode(root, arr[i]);` `    ``cout << maximumElement(root, a, b) << endl;` `    ``return` `0;``}`

## Java

 `// Java program to find maximum element in the path``// between two Nodes of Binary Search Tree.``class` `Solution``{``    ` `static` `class` `Node``{``     ``Node left, right;``    ``int` `data;``}`` ` `// Create and return a pointer of new Node.``static` `Node createNode(``int` `x)``{``    ``Node p = ``new` `Node();``    ``p . data = x;``    ``p . left = p . right = ``null``;``    ``return` `p;``}`` ` `// Insert a new Node in Binary Search Tree.``static` `void` `insertNode( Node root, ``int` `x)``{``    ``Node p = root, q = ``null``;`` ` `    ``while` `(p != ``null``)``    ``{``        ``q = p;``        ``if` `(p . data < x)``            ``p = p . right;``        ``else``            ``p = p . left;``    ``}`` ` `    ``if` `(q == ``null``)``        ``p = createNode(x);``    ``else``    ``{``        ``if` `(q . data < x)``            ``q . right = createNode(x);``        ``else``            ``q . left = createNode(x);``    ``}``}`` ` `// Return the maximum element between a Node``// and its given ancestor.``static` `int` `maxelpath(Node q, ``int` `x)``{``    ``Node p = q;`` ` `    ``int` `mx = -``1``;`` ` `    ``// Traversing the path between ancestor and``    ``// Node and finding maximum element.``    ``while` `(p . data != x)``    ``{``        ``if` `(p . data > x)``        ``{``            ``mx = Math.max(mx, p . data);``            ``p = p . left;``        ``}``        ``else``        ``{``            ``mx = Math.max(mx, p . data);``            ``p = p . right;``        ``}``    ``}`` ` `    ``return` `Math.max(mx, x);``}`` ` `// Return maximum element in the path between``// two given Node of BST.``static` `int` `maximumElement( Node root, ``int` `x, ``int` `y)``{``    ``Node p = root;`` ` `    ``// Finding the LCA of Node x and Node y``    ``while` `((x < p . data && y < p . data) ||``        ``(x > p . data && y > p . data))``    ``{``        ``// Checking if both the Node lie on the``        ``// left side of the parent p.``        ``if` `(x < p . data && y < p . data)``            ``p = p . left;`` ` `        ``// Checking if both the Node lie on the``        ``// right side of the parent p.``        ``else` `if` `(x > p . data && y > p . data)``            ``p = p . right;``    ``}`` ` `    ``// Return the maximum of maximum elements occur``    ``// in path from ancestor to both Node.``    ``return` `Math.max(maxelpath(p, x), maxelpath(p, y));``}`` ` ` ` `// Driver Code``public` `static` `void` `main(String args[])``{``    ``int` `arr[] = { ``18``, ``36``, ``9``, ``6``, ``12``, ``10``, ``1``, ``8` `};``    ``int` `a = ``1``, b = ``10``;``    ``int` `n =arr.length;`` ` `    ``// Creating the root of Binary Search Tree``     ``Node root = createNode(arr[``0``]);`` ` `    ``// Inserting Nodes in Binary Search Tree``    ``for` `(``int` `i = ``1``; i < n; i++)``        ``insertNode(root, arr[i]);`` ` `    ``System.out.println( maximumElement(root, a, b) );`` ` `}``}``//contributed by Arnab Kundu`

## Python3

 `# Python 3 program to find maximum element``# in the path between two Nodes of Binary``# Search Tree.` `# Create and return a pointer of new Node.``class` `createNode:` `    ``# Constructor to create a new node``    ``def` `__init__(``self``, data):``        ``self``.data ``=` `data``        ``self``.left ``=` `None``        ``self``.right ``=` `None` `# Insert a new Node in Binary Search Tree.``def` `insertNode(root, x):``    ``p, q ``=` `root, ``None` `    ``while` `p !``=` `None``:``        ``q ``=` `p``        ``if` `p.data < x:``            ``p ``=` `p.right``        ``else``:``            ``p ``=` `p.left` `    ``if` `q ``=``=` `None``:``        ``p ``=` `createNode(x)``    ``else``:``        ``if` `q.data < x:``            ``q.right ``=` `createNode(x)``        ``else``:``            ``q.left ``=` `createNode(x)` `# Return the maximum element between a``# Node and its given ancestor.``def` `maxelpath(q, x):``    ``p ``=` `q` `    ``mx ``=` `-``999999999999` `    ``# Traversing the path between ancestor``    ``# and Node and finding maximum element.``    ``while` `p.data !``=` `x:``        ``if` `p.data > x:``            ``mx ``=` `max``(mx, p.data)``            ``p ``=` `p.left``        ``else``:``            ``mx ``=` `max``(mx, p.data)``            ``p ``=` `p.right` `    ``return` `max``(mx, x)` `# Return maximum element in the path``# between two given Node of BST.``def` `maximumElement(root, x, y):``    ``p ``=` `root` `    ``# Finding the LCA of Node x and Node y``    ``while` `((x < p.data ``and` `y < p.data) ``or``           ``(x > p.data ``and` `y > p.data)):``               ` `        ``# Checking if both the Node lie on``        ``# the left side of the parent p.``        ``if` `x < p.data ``and` `y < p.data:``            ``p ``=` `p.left` `        ``# Checking if both the Node lie on``        ``# the right side of the parent p.``        ``elif` `x > p.data ``and` `y > p.data:``            ``p ``=` `p.right` `    ``# Return the maximum of maximum elements``    ``# occur in path from ancestor to both Node.``    ``return` `max``(maxelpath(p, x), maxelpath(p, y))` `# Driver Code``if` `__name__ ``=``=` `'__main__'``:``    ``arr ``=` `[ ``18``, ``36``, ``9``, ``6``, ``12``, ``10``, ``1``, ``8``]``    ``a, b ``=` `1``, ``10``    ``n ``=` `len``(arr)` `    ``# Creating the root of Binary Search Tree``    ``root ``=` `createNode(arr[``0``])` `    ``# Inserting Nodes in Binary Search Tree``    ``for` `i ``in` `range``(``1``,n):``        ``insertNode(root, arr[i])` `    ``print``(maximumElement(root, a, b))` `# This code is contributed by PranchalK`

## C#

 `using` `System;` `// C# program to find maximum element in the path``// between two Nodes of Binary Search Tree.``public` `class` `Solution``{` `public` `class` `Node``{``     ``public` `Node left, right;``    ``public` `int` `data;``}` `// Create and return a pointer of new Node.``public` `static` `Node createNode(``int` `x)``{``    ``Node p = ``new` `Node();``    ``p.data = x;``    ``p.left = p.right = ``null``;``    ``return` `p;``}` `// Insert a new Node in Binary Search Tree.``public` `static` `void` `insertNode(Node root, ``int` `x)``{``    ``Node p = root, q = ``null``;` `    ``while` `(p != ``null``)``    ``{``        ``q = p;``        ``if` `(p.data < x)``        ``{``            ``p = p.right;``        ``}``        ``else``        ``{``            ``p = p.left;``        ``}``    ``}` `    ``if` `(q == ``null``)``    ``{``        ``p = createNode(x);``    ``}``    ``else``    ``{``        ``if` `(q.data < x)``        ``{``            ``q.right = createNode(x);``        ``}``        ``else``        ``{``            ``q.left = createNode(x);``        ``}``    ``}``}` `// Return the maximum element between a Node``// and its given ancestor.``public` `static` `int` `maxelpath(Node q, ``int` `x)``{``    ``Node p = q;` `    ``int` `mx = -1;` `    ``// Traversing the path between ancestor and``    ``// Node and finding maximum element.``    ``while` `(p.data != x)``    ``{``        ``if` `(p.data > x)``        ``{``            ``mx = Math.Max(mx, p.data);``            ``p = p.left;``        ``}``        ``else``        ``{``            ``mx = Math.Max(mx, p.data);``            ``p = p.right;``        ``}``    ``}` `    ``return` `Math.Max(mx, x);``}` `// Return maximum element in the path between``// two given Node of BST.``public` `static` `int` `maximumElement(Node root, ``int` `x, ``int` `y)``{``    ``Node p = root;` `    ``// Finding the LCA of Node x and Node y``    ``while` `((x < p.data && y < p.data) || (x > p.data && y > p.data))``    ``{``        ``// Checking if both the Node lie on the``        ``// left side of the parent p.``        ``if` `(x < p.data && y < p.data)``        ``{``            ``p = p.left;``        ``}` `        ``// Checking if both the Node lie on the``        ``// right side of the parent p.``        ``else` `if` `(x > p.data && y > p.data)``        ``{``            ``p = p.right;``        ``}``    ``}` `    ``// Return the maximum of maximum elements occur``    ``// in path from ancestor to both Node.``    ``return` `Math.Max(maxelpath(p, x), maxelpath(p, y));``}`  `// Driver Code``public` `static` `void` `Main(``string``[] args)``{``    ``int``[] arr = ``new` `int``[] {18, 36, 9, 6, 12, 10, 1, 8};``    ``int` `a = 1, b = 10;``    ``int` `n = arr.Length;` `    ``// Creating the root of Binary Search Tree``     ``Node root = createNode(arr[0]);` `    ``// Inserting Nodes in Binary Search Tree``    ``for` `(``int` `i = 1; i < n; i++)``    ``{``        ``insertNode(root, arr[i]);``    ``}` `    ``Console.WriteLine(maximumElement(root, a, b));` `}``}` `  ``//  This code is contributed by Shrikant13`

## Javascript

 ``

Output

`12`

Time complexity: O(h), where h is the height of BST
Auxiliary Space: O(1)

This article is contributed by Anuj Chauhan. If you like GeeksforGeeks and would like to contribute, you can also write an article using write.geeksforgeeks.org or mail your article to review-team@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

My Personal Notes arrow_drop_up