Maximum element between two nodes of BST in C++

Problem statement

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

Example

If array is {24, 23, 15, 36, 19, 41, 25, 35} the we can form BST as follows −

If we consider A = 19 and B = 41 then maximum element between these two nodes is 41

Algorithm

Find Lowest Common Ancestor(LCA) of node A and B.
Find maximum node between LCA and A. Let us call it as max1
Find maximum node between LCA and B. Let us call it as max2
Return maximum of max1 and max2

Example

Let us now see an example −

Live Demo

#include <bits/stdc++.h>
using namespace std;
struct node {
   int data;
   struct node* left;
   struct node* right;
};
node *createNode(int x) {
   node *p = new node();
   p -> data = x;
   p -> left = NULL;
   p -> right = NULL;
   return p;
}
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);
      }
   }
}
int maxelpath(node *q, int x) {
   node *p = q;
   int mx = INT_MIN;
   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);
}
int getMaximumElement(struct node *root, int x, int y) {
   node *p = root;
   while ((x < p -> data && y < p -> data) || (x > p ->
   data && y > p -> data)) {
      if (x < p -> data && y < p -> data) {
         p = p -> left;
      } else if (x > p -> data && y > p -> data) {
         p = p -> right;
      }
   }
   return max(maxelpath(p, x), maxelpath(p, y));
}
int main() {
   int arr[] = {24, 23, 15, 36, 19, 41, 25, 35}; int a = 19, b = 41;
   int n = sizeof(arr) / sizeof(arr[0]);
   struct node *root = createNode(arr[0]);
   for (int i = 1; i < n; i++) insertNode(root, arr[i]);
   cout << "Maximum element = " << getMaximumElement(root, a, b) << endl;
   return 0;
}