Find the maximum node at a given level in a binary tree

Given a Binary Tree and a Level. The task is to find the node with the maximum value at that given level.

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

The idea is to traverse the tree along depth recursively and return the nodes once the required level is reached and then return the maximum of left and right subtrees for each subsequent call. So that the last call will return the node with maximum value among all nodes at the given level.

Below is the step by step algorithm:

Perform DFS traversal and every time decrease the value of level by 1 and keep traversing to the left and right subtrees recursively.
When value of level becomes 0, it means we are on the given level, then return root->data.
Find the maximum between the two values returned by left and right subtrees and return the maximum.

Below is the implementation of above approach:

C++

// CPP program to find the node with 
// maximum value at a given level 
  
#include <iostream> 
  
using namespace std; 
  
// Tree node 
struct Node { 
    int data; 
    struct Node *left, *right; 
}; 
  
// Utility function to create a new Node 
struct Node* newNode(int val) 
{ 
    struct Node* temp = new Node; 
    temp->left = NULL; 
    temp->right = NULL; 
    temp->data = val; 
    return temp; 
} 
  
// function to find the maximum value 
// at given level 
int maxAtLevel(struct Node* root, int level) 
{ 
    // If the tree is empty 
    if (root == NULL) 
        return 0; 
  
    // if level becomes 0, it means we are on 
    // any node at the given level 
    if (level == 0) 
        return root->data; 
  
    int x = maxAtLevel(root->left, level - 1); 
    int y = maxAtLevel(root->right, level - 1); 
  
    // return maximum of two 
    return max(x, y); 
} 
  
// Driver code 
int main() 
{ 
    // Creating the tree 
    struct Node* root = NULL; 
    root = newNode(45); 
    root->left = newNode(46); 
    root->left->left = newNode(18); 
    root->left->left->left = newNode(16); 
    root->left->left->right = newNode(23); 
    root->left->right = newNode(17); 
    root->left->right->left = newNode(24); 
    root->left->right->right = newNode(21); 
    root->right = newNode(15); 
    root->right->left = newNode(22); 
    root->right->left->left = newNode(37); 
    root->right->left->right = newNode(41); 
    root->right->right = newNode(19); 
    root->right->right->left = newNode(49); 
    root->right->right->right = newNode(29); 
  
    int level = 3; 
  
    cout << maxAtLevel(root, level); 
  
    return 0; 
} 

Java

// Java program to find the  
// node with maximum value  
// at a given level 
import java.util.*; 
class GFG 
{ 
  
// Tree node 
static class Node  
{ 
    int data; 
    Node left, right; 
} 
  
// Utility function to 
// create a new Node 
static Node newNode(int val) 
{ 
    Node temp = new Node(); 
    temp.left = null; 
    temp.right = null; 
    temp.data = val; 
    return temp; 
} 
  
// function to find  
// the maximum value 
// at given level 
static int maxAtLevel(Node root, int level) 
{ 
    // If the tree is empty 
    if (root == null) 
        return 0; 
  
    // if level becomes 0,  
    // it means we are on 
    // any node at the given level 
    if (level == 0) 
        return root.data; 
  
    int x = maxAtLevel(root.left, level - 1); 
    int y = maxAtLevel(root.right, level - 1); 
  
    // return maximum of two 
    return Math.max(x, y); 
} 
  
// Driver code 
public static void main(String args[]) 
{ 
    // Creating the tree 
    Node root = null; 
    root = newNode(45); 
    root.left = newNode(46); 
    root.left.left = newNode(18); 
    root.left.left.left = newNode(16); 
    root.left.left.right = newNode(23); 
    root.left.right = newNode(17); 
    root.left.right.left = newNode(24); 
    root.left.right.right = newNode(21); 
    root.right = newNode(15); 
    root.right.left = newNode(22); 
    root.right.left.left = newNode(37); 
    root.right.left.right = newNode(41); 
    root.right.right = newNode(19); 
    root.right.right.left = newNode(49); 
    root.right.right.right = newNode(29); 
  
    int level = 3; 
  
    System.out.println(maxAtLevel(root, level)); 
} 
} 
  
// This code is contributed 
// by Arnab Kundu 

Python3

# Python3 program to find the node   
# with maximum value at a given level  
  
# Helper function that allocates a new  
# node with the given data and None  
# left and right poers.                                      
class newNode:  
  
    # Constructor to create a new node  
    def __init__(self, data):  
        self.data = data 
        self.left = None
        self.right = None
  
# function to find the maximum   
# value at given level  
def maxAtLevel(root, level):  
  
    # If the tree is empty  
    if (root == None) : 
        return 0
  
    # if level becomes 0, it means we  
    # are on any node at the given level  
    if (level == 0) : 
        return root.data  
  
    x = maxAtLevel(root.left, level - 1)  
    y = maxAtLevel(root.right, level - 1)  
  
    # return maximum of two  
    return max(x, y) 
      
# Driver Code  
if __name__ == '__main__': 
  
    """  
    Let us create Binary Tree shown 
    in above example """
    root = newNode(45)  
    root.left = newNode(46)  
    root.left.left = newNode(18)  
    root.left.left.left = newNode(16)  
    root.left.left.right = newNode(23)  
    root.left.right = newNode(17)  
    root.left.right.left = newNode(24)  
    root.left.right.right = newNode(21)  
    root.right = newNode(15)  
    root.right.left = newNode(22)  
    root.right.left.left = newNode(37)  
    root.right.left.right = newNode(41)  
    root.right.right = newNode(19)  
    root.right.right.left = newNode(49)  
    root.right.right.right = newNode(29) 
    level = 3
    print(maxAtLevel(root, level)) 
  
# This code is contributed by 
# Shubham Singh(SHUBHAMSINGH10) 

C#

// C# program to find the  
// node with maximum value  
// at a given level 
using System; 
  
class GFG 
{ 
  
    // Tree node 
    class Node  
    { 
        public int data; 
        public Node left, right; 
    } 
  
    // Utility function to 
    // create a new Node 
    static Node newNode(int val) 
    { 
        Node temp = new Node(); 
        temp.left = null; 
        temp.right = null; 
        temp.data = val; 
        return temp; 
    } 
  
    // function to find  
    // the maximum value 
    // at given level 
    static int maxAtLevel(Node root, int level) 
    { 
        // If the tree is empty 
        if (root == null) 
            return 0; 
  
        // if level becomes 0,  
        // it means we are on 
        // any node at the given level 
        if (level == 0) 
            return root.data; 
  
        int x = maxAtLevel(root.left, level - 1); 
        int y = maxAtLevel(root.right, level - 1); 
  
        // return maximum of two 
        return Math.Max(x, y); 
    } 
  
    // Driver code 
    public static void Main(String []args) 
    { 
        // Creating the tree 
        Node root = null; 
        root = newNode(45); 
        root.left = newNode(46); 
        root.left.left = newNode(18); 
        root.left.left.left = newNode(16); 
        root.left.left.right = newNode(23); 
        root.left.right = newNode(17); 
        root.left.right.left = newNode(24); 
        root.left.right.right = newNode(21); 
        root.right = newNode(15); 
        root.right.left = newNode(22); 
        root.right.left.left = newNode(37); 
        root.right.left.right = newNode(41); 
        root.right.right = newNode(19); 
        root.right.right.left = newNode(49); 
        root.right.right.right = newNode(29); 
  
        int level = 3; 
  
        Console.WriteLine(maxAtLevel(root, level)); 
    } 
} 
  
// This code is contributed by 29AjayKumar 

Output:

My Personal Notes

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

C++

Java

Python3

C#

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