• Skip to primary navigation
  • Skip to content
  • Skip to primary sidebar
  • Skip to secondary sidebar

GoHired

Interview Questions asked in Google, Microsoft, Amazon

Join WeekEnd Online Batch from 4-April-2020 on How to Crack Coding Interview in Just 10 Weeks : Fees just 20,000 INR

  • Home
  • Best Java Books
  • Algorithm
  • Internship
  • Certificates
  • About Us
  • Contact Us
  • Privacy Policy
  • Array
  • Stack
  • Queue
  • LinkedList
  • DP
  • Strings
  • Tree
  • Mathametical
  • Puzzles
  • Graph

Handle duplicates in Binary Search Tree

April 17, 2017 by Dhaval Dave

In a Binary Search Tree (BST), all keys in left subtree of a key must be smaller and all keys in right subtree must be greater. So a Binary Search Tree by definition has distinct keys and duplicates in binary search tree are not allowed.

How to allow duplicates where every insertion inserts one more key with a value and every deletion deletes one occurrence?

A Simple Solution is to allow same keys with count. For example consider insertion of keys 3, 6, 7, 8, 8, 8, 10, 12, 12 in an empty Binary Search Tree

         8(3)
       /     \      
    6(1)      10(1)
  /    \        \
3(1)    7(1)     12(2)

This count store requires changing the structure of Binary Search tree to

struct node
{
    int key;
    int count;
    struct node *left, *right;
};

And We may need to change the code of Functions of “Insert” “Find” and “Delete”.

Lets see for Insert

struct node* insert(struct node* node, int key)
{
    if (node == NULL) return newNode(key);
 
    if (key == node->key)
    {
       (node->count)++;
        return node;
    }
 
    if (key < node->key)
        node->left  = insert(node->left, key);
    else
        node->right = insert(node->right, key);
 
    return node;
}

Now Based upon Above code You can try to write code for “Search a value in BST with Duplicate” and Delete a node in BST with duplicate”.
PS : In delete a node in BST, Handling of adjusment of tree branches should happen.

Solution 2 :

If change in Structure of Binary Search Tree is not allowed, We can think of Extra memory like Hashmap to keep the count of nodes of BST to support duplicates in Binary Search Tree. ie Hashmap below is with above tree without count.

 3 - 1
 6 - 1
 7 - 1
 8 - 3
10 - 1
12 - 2

Solution 3:

We can think of keeping same keys on left side (we could also choose right side) to support duplicates in Binary Search Tree. For example consider insertion of keys 3, 6, 7, 8, 8, 8, 10, 12, 12  in an empty Binary Search Tree

              8
          /       \
        8         12
      /           /     \
    8           10      12
  /
 6   
/  \
3  7

 

 

Similar Articles

Filed Under: Amazon Interview Question, Flipkart Interview Questions, Hacker Earth Questions, Interview Questions, Microsoft Interview Questions, problem Tagged With: Binary Search Tree, Binary Tree

Reader Interactions

Primary Sidebar

Join WeekEnd Online/Offline Batch from 4-April-2020 on How to Crack Coding Interview in Just 10 Weeks : Fees just 20,000 INR

Join WeekEnd Online/Offline Batch from 4-April-2020

WhatsApp us

Secondary Sidebar

Custom Search

  • How I cracked AMAZON
  • LeetCode
  • Adobe
  • Amazon
  • Facebook
  • Microsoft
  • Hacker Earth
  • CSE Interview

Top Rated Questions

Level order traversal in Spiral form

Common Ancestor in a Binary Tree or Binary Search Tree

CodeChef’ RRCOPY

Reverse a Linked List in groups of given size

Find the element that appears once others appears thrice

Given a string, find the first character which is non-repetitive

Skiing on Mountains Matrix

Find the number ABCD such that when multipled by 4 gives DCBA.

Password Predictor

Printing each word reverse in string

Reliance Jio Software Developer Interview Experience

Get Minimum element in O(1) from input numbers or Stack

Walmart Labs Interview Experience

Python List

Wrong Directions given find minimum moves so that he can reach to the destination

flattens 2 D linked list to a single sorted link list

Daughter’s Age VeryGood Puzzle

ADOBE Aptitude C Language Test

strtok()

Maximum sum contiguous subarray of an Array

C Program for TAIL command of UNIX

Interfaces in C++ (Abstract Classes in C++)

VMWare SDEII Interview

Stickler thief

LeetCode: Binary Tree Maximum Path Sum

Amazon Interview Experience – SDE Chennai

Serialise Deserialise N-ary Tree

Implement a generic binary search algorithm for Integer Double String etc

Find next greater number with same set of digits

N Petrol bunks or City arranged in circle. You have Fuel and distance between petrol bunks. Is it possible to find starting point so that we can travel all Petrol Bunks

Copyright © 2025 · Genesis Framework · WordPress · Log in