The Java Algorithms online test assesses candidates' algorithmic-thinking skills and their ability to implement algorithms using Java.

It's an ideal test for pre-employment screening. A good developer will be able to design and implement algorithms that are both correct and efficient. Computational complexity is important not only when scaling applications but when creating responsive, maintainable, and efficient code.

This online test requires candidates to analyze or design an algorithm using Java as the programming language.

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Sample Free Questions

Binary Search Tree

15min
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Easy  
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CODE

Java Algorithmic thinking Data structures Public

A three-node binary tree.Binary search tree (BST) is a binary tree where the value of each node is larger or equal to the values in all the nodes in that node's left subtree and is smaller than the values in all the nodes in that node's right subtree.

Write a function that, efficiently with respect to time used, checks if a given binary search tree contains a given value.

For example, for the following tree:

  • n1 (Value: 1, Left: null, Right: null)
  • n2 (Value: 2, Left: n1, Right: n3)
  • n3 (Value: 3, Left: null, Right: null)

Call to contains(n2, 3) should return true since a tree with root at n2 contains number 3.

Two Sum

30min
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Easy  
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CODE

Java Algorithmic thinking Searching Public

Write a function that, when passed a list and a target sum, returns, efficiently with respect to time used, two distinct zero-based indices of any two of the numbers, whose sum is equal to the target sum. If there are no two numbers, the function should return null.

For example, findTwoSum(new int[] { 3, 1, 5, 7, 5, 9 }, 10) should return a single dimensional array with two elements and contain any of the following pairs of indices:

  • 0 and 3 (or 3 and 0) as 3 + 7 = 10
  • 1 and 5 (or 5 and 1) as 1 + 9 = 10
  • 2 and 4 (or 4 and 2) as 5 + 5 = 10

Sorted Search

20min
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Hard  
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CODE

Java Algorithmic thinking Searching Public

Implement function countNumbers that accepts a sorted array of unique integers and, efficiently with respect to time used, counts the number of array elements that are less than the parameter lessThan.

For example, SortedSearch.countNumbers(new int[] { 1, 3, 5, 7 }, 4) should return 2 because there are two array elements less than 4.

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Utilities, Runner, Document Store, Needle, Log Parser, Driver Exam, Crop Ratio, Programmer Teacher, Chicken, Paragraph, Username, Chain Link, Hobbies, Read First Line, Node, Shipping, Racer, Snapshot, Date Transform, Segment, Internal Nodes, Moving Total, Entry, Unique Numbers, Remove Repetitions, Max Sum, Unique Name, Friend, Paper Strip, Stories, Train, Platformer, Weighted Average, Test Results, Product, Unloading Trucks, Shelf, Rare, Stack to List, Read Write Execute, Shining Star, Document Counter, Snow Storm
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Java OOP Bug fixing Memory management Language Stream Strings Serialization Exceptions Data structures Arrays Iteration Arithmetic Multithreading Algorithmic thinking Searching Graphs Dynamic programming Refactoring Sorting Test case design TDD
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