Find maximum (or minimum) in Binary Tree

Given a Binary Tree, find the maximum(or minimum) element in it. For example, maximum in the following Binary Tree is 9.

Recommended: Please solve it on “PRACTICE” first, before moving on to the solution.

In Binary Search Tree, we can find maximum by traversing right pointers until we reach the rightmost node. But in Binary Tree, we must visit every node to figure out maximum. So the idea is to traverse the given tree and for every node return maximum of 3 values.
1) Node’s data.
2) Maximum in node’s left subtree.
3) Maximum in node’s right subtree.

Below is the implementation of above approach.

CPP

// C++ program to find maximum and  
// minimum in a Binary Tree  
#include<bits/stdc++.h>  
#include<iostream> 
using namespace std;  
  
// A tree node  
class Node  
{  
    public: 
    int data;  
    Node* left, *right;  
      
    /* Constructor that allocates a new  
    node with the given data and NULL  
    left and right pointers. */
    Node(int data) 
    { 
        this->data = data; 
        this->left = NULL; 
        this->right = NULL; 
    } 
};  
  
// Returns maximum value in a given  
// Binary Tree  
int findMax(Node* root)  
{  
    // Base case  
    if (root == NULL)  
    return INT_MIN;  
  
    // Return maximum of 3 values:  
    // 1) Root's data 2) Max in Left Subtree  
    // 3) Max in right subtree  
    int res = root->data;  
    int lres = findMax(root->left);  
    int rres = findMax(root->right);  
    if (lres > res)  
    res = lres;  
    if (rres > res)  
    res = rres;  
    return res;  
}  
  
// Driver Code 
int main()  
{  
    Node*NewRoot = NULL;  
    Node *root = new Node(2);  
    root->left = new Node(7);  
    root->right = new Node(5);  
    root->left->right = new Node(6);  
    root->left->right->left = new Node(1);  
    root->left->right->right = new Node(11);  
    root->right->right = new Node(9);  
    root->right->right->left = new Node(4);  
  
    cout << "Maximum element is " 
         << findMax(root) << endl;  
  
    return 0;  
}  
  
// This code is contributed by 
// rathbhupendra 

C

// C program to find maximum and minimum in a Binary Tree 
#include <stdio.h> 
#include <stdlib.h> 
#include <limits.h> 
  
// A tree node 
struct Node 
{ 
    int data; 
    struct Node* left, *right; 
}; 
  
// A utility function to create a new node 
struct Node* newNode(int data) 
{ 
    struct Node* node = (struct Node*) 
                        malloc(sizeof(struct Node)); 
    node->data = data; 
    node->left = node->right = NULL; 
    return(node); 
} 
  
// Returns maximum value in a given Binary Tree 
int findMax(struct Node* root) 
{ 
    // Base case 
    if (root == NULL) 
      return INT_MIN; 
  
    // Return maximum of 3 values: 
    // 1) Root's data 2) Max in Left Subtree 
    // 3) Max in right subtree 
    int res = root->data; 
    int lres = findMax(root->left); 
    int rres = findMax(root->right); 
    if (lres > res) 
      res = lres; 
    if (rres > res) 
      res = rres; 
    return res; 
} 
  
// Driver program 
int main(void) 
{ 
    struct Node*NewRoot=NULL; 
    struct Node *root = newNode(2); 
    root->left        = newNode(7); 
    root->right       = newNode(5); 
    root->left->right = newNode(6); 
    root->left->right->left=newNode(1); 
    root->left->right->right=newNode(11); 
    root->right->right=newNode(9); 
    root->right->right->left=newNode(4); 
  
    printf ("Maximum element is %d \n", findMax(root)); 
  
    return 0; 
} 

Java

// Java code to Find maximum (or minimum) in  
// Binary Tree 
  
// A binary tree node 
class Node { 
    int data; 
    Node left, right; 
  
public Node(int data) 
    { 
        this.data = data; 
        left = right = null; 
    } 
} 
  
class BinaryTree { 
    Node root; 
  
    // Returns the max value in a binary tree 
    static int findMax(Node node) 
    { 
        if (node == null) 
            return Integer.MIN_VALUE; 
  
        int res = node.data; 
        int lres = findMax(node.left); 
        int rres = findMax(node.right); 
  
        if (lres > res) 
            res = lres; 
        if (rres > res) 
            res = rres; 
        return res; 
    } 
  
    /* Driver program to test above functions */
    public static void main(String args[]) 
    { 
        BinaryTree tree = new BinaryTree(); 
        tree.root = new Node(2); 
        tree.root.left = new Node(7); 
        tree.root.right = new Node(5); 
        tree.root.left.right = new Node(6); 
        tree.root.left.right.left = new Node(1); 
        tree.root.left.right.right = new Node(11); 
        tree.root.right.right = new Node(9); 
        tree.root.right.right.left = new Node(4); 
  
        System.out.println("Maximum element is " + 
                         tree.findMax(tree.root)); 
    } 
} 
  
// This code is contributed by Kamal Rawal 

Python3

# Python3 program to find maximum 
# and minimum in a Binary Tree 
  
# A class to create a new node  
class newNode: 
    def __init__(self, data): 
        self.data = data  
        self.left = self.right = None
      
# Returns maximum value in a  
# given Binary Tree  
def findMax(root): 
      
    # Base case  
    if (root == None):  
        return float('-inf') 
  
    # Return maximum of 3 values:  
    # 1) Root's data 2) Max in Left Subtree  
    # 3) Max in right subtree  
    res = root.data 
    lres = findMax(root.left)  
    rres = findMax(root.right)  
    if (lres > res): 
        res = lres  
    if (rres > res):  
        res = rres  
    return res 
  
# Driver Code 
if __name__ == '__main__': 
    root = newNode(2)  
    root.left     = newNode(7)  
    root.right     = newNode(5)  
    root.left.right = newNode(6)  
    root.left.right.left=newNode(1)  
    root.left.right.right=newNode(11)  
    root.right.right=newNode(9)  
    root.right.right.left=newNode(4)  
  
    print("Maximum element is",  
                 findMax(root))  
  
# This code is contributed by PranchalK 

C#

using System; 
  
// C# code to Find maximum (or minimum) in   
// Binary Tree  
  
// A binary tree node  
public class Node 
{ 
    public int data; 
    public Node left, right; 
  
public Node(int data) 
{ 
        this.data = data; 
        left = right = null; 
} 
} 
  
public class BinaryTree 
{ 
    public Node root; 
  
    // Returns the max value in a binary tree  
    public static int findMax(Node node) 
    { 
        if (node == null) 
        { 
            return int.MinValue; 
        } 
  
        int res = node.data; 
        int lres = findMax(node.left); 
        int rres = findMax(node.right); 
  
        if (lres > res) 
        { 
            res = lres; 
        } 
        if (rres > res) 
        { 
            res = rres; 
        } 
        return res; 
    } 
  
    /* Driver program to test above functions */
    public static void Main(string[] args) 
    { 
        BinaryTree tree = new BinaryTree(); 
        tree.root = new Node(2); 
        tree.root.left = new Node(7); 
        tree.root.right = new Node(5); 
        tree.root.left.right = new Node(6); 
        tree.root.left.right.left = new Node(1); 
        tree.root.left.right.right = new Node(11); 
        tree.root.right.right = new Node(9); 
        tree.root.right.right.left = new Node(4); 
  
        Console.WriteLine("Maximum element is " + BinaryTree.findMax(tree.root)); 
    } 
} 
  
  // This code is contributed by Shrikant13 

Output:

Maximum element is 11

Similarly, we can find the minimum element in a Binary tree by comparing three values. Below is the function to find a minimum in Binary Tree.

C

// Returns minimum value in a given Binary Tree 
int findMin(struct Node* root) 
{ 
    // Base case 
    if (root == NULL) 
      return INT_MAX; 
  
    // Return minimum of 3 values: 
    // 1) Root's data 2) Max in Left Subtree 
    // 3) Max in right subtree 
    int res = root->data; 
    int lres = findMin(root->left); 
    int rres = findMin(root->right); 
    if (lres < res) 
      res = lres; 
    if (rres < res) 
      res = rres; 
    return res; 
} 

Java

// Returns the min value in a binary tree 
static int findMin(Node node) 
{ 
    if (node == null) 
        return Integer.MAX_VALUE; 
  
    int res = node.data; 
    int lres = findMin(node.left); 
    int rres = findMin(node.right); 
  
    if (lres < res) 
        res = lres; 
    if (rres < res) 
        res = rres; 
    return res; 
} 

Python3

# Returns the min value in a binary tree 
  
def find_min_in_BT(root): 
    if root is None: 
        return float('inf') 
    res = root.data 
    lres = find_min_in_BT(root.leftChild) 
    rres = find_min_in_BT(root.rightChild) 
    if lres < res: 
        res = lres 
    if rres < res: 
        res = rres 
    return res 
  
# This code is contributed by Subhajit Nandi 

C#

// Returns the min value in a binary tree 
public static int findMin(Node node) 
{ 
    if (node == null) 
        return int.MaxValue; 
  
    int res = node.data; 
    int lres = findMin(node.left); 
    int rres = findMin(node.right); 
  
    if (lres < res) 
        res = lres; 
    if (rres < res) 
        res = rres; 
    return res; 
} 
  
// This code is contributed by Code_Mech 

This article is contributed by Himanshu Gupta. Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.

GeeksforGeeks has prepared a complete interview preparation course with premium videos, theory, practice problems, TA support and many more features. Please refer Placement 100 for details

My Personal Notes

Recommended: Please solve it on “PRACTICE” first, before moving on to the solution.

CPP

C

Java

Python3

C#

C

Java

Python3

C#

Recommended Posts: