Find the node with maximum value in a Binary Search Tree

Given a Binary Search Tree, the task is to find the node with the maximum value in a BST.


For the above tree, we start with 20, then we move right 22, we keep on moving to right until we see NULL. Since right of 22 is NULL, 22 is the node with maximum value.

Approach: This is quite simple. Just traverse the node from root to right recursively until right is NULL. The node whose right is NULL is the node with maximum value.

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#include <bits/stdc++.h>
using namespace std;
  
/* A binary tree node has data, pointer to left child  
   and a pointer to right child */
struct node {
    int data;
    struct node* left;
    struct node* right;
};
  
// 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 = NULL;
    node->right = NULL;
  
    return (node);
}
  
// Function to insert a new node in BST
struct node* insert(struct node* node, int data)
{
    /* 1. If the tree is empty, return a new,      
      single node */
    if (node == NULL)
        return (newNode(data));
    else {
        /* 2. Otherwise, recur down the tree */
        if (data <= node->data)
            node->left = insert(node->left, data);
        else
            node->right = insert(node->right, data);
  
        /* return the (unchanged) node pointer */
        return node;
    }
}
  
// Function to find the node with maximum value
// i.e. rightmost leaf node
int maxValue(struct node* node)
{   
    /* loop down to find the rightmost leaf */
    struct node* current = node;
    while (current->right != NULL) 
        current = current->right;
      
    return (current->data);
}
  
// Driver code
int main()
{
    struct node* root = NULL;
    root = insert(root, 4);
    insert(root, 2);
    insert(root, 1);
    insert(root, 3);
    insert(root, 6);
    insert(root, 5);
  
    cout << "Maximum value in BST is " << maxValue(root);
  
    return 0;
}

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Output:

Maximum value in BST is 6


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