Question

Implement a method to count in a BST, all keys that are within a given range. Assume that keys in the BST are unique i.e there are no duplicates. Must use recursion and no helper methods.

Public class BSTNode{

int key;

BSTNode left, right;

...

}

//count number of keys in BST that are in the range low to high, inclusive all k suck that low <= k <= high

public static int countInRange(BSTNode root, int low, int high){

//COMPLETE METHOD

}

Answer 1

//Java code

public static int countInRange(BSTNode root, int low, int high)
{
   // Base case
   if (root == null) return 0;
  
   // If current node is in range, then include it in count and recur for left and right children of it
   if (root.key <= high && root.key >= low)
       return 1 + countInRange(root.left, low, high) + countInRange(root.right, low, high);
  
   else
       return countInRange(root.left, low, high) + countInRange(root.right, low, high);
  
}