Write a program to reverse a singly linked list? Modify that program to reverse a doubly linked list.
Java Interview Questions
Print out the prime numbers between 1 and 100. As a first pass, don't worry about writing an efficient algorithm. Just write clear code that is easy to follow. Once you've done that, consider different possible optimizations.
Use Newton's method to approximate the square root of a method. Newton's method is to approximate z = Sqrt(x) by picking a starting point z and then repeating:
z = z - (z*z - x)/(2*z)
Pick a sensible point to stop the iteration.
Most languages have a built in sort method that will sort an array of strings alphabetically. Demonstrate how to sort an array of strings by the length of each string, shortest strings first.
Suppose you have a web form that allows users to upload JPG, GIF or PNG images. Before you store the images in your system, you want to convert them all to the JPG format. Design an image converter API. Sketch out all classes and interfaces that are involved.
Note: the actual code necessary to convert a JPG image to a GIF image is not the point. Just place a comment at the appropriate location where the actual conversion should occur.
Assume that you have access to an employee's email Inbox, and that you can parse the content of their emails, including the email headers.
- How can you use this to deduce their first-degree connections?
- What kind of heuristics can you come up with to quantify the strength of these first-degree connections?
- How can you use this to deduce their second-degree connections?
- How can you use this to deduce their third-degree connections?
Suppose you have an array of 99 numbers. The array contains the digits 1 to 100 with one digit missing. Describe four different algorithms to compute the missing number. Two of these should optimize for low storage and two of these should optimize for fast processing.
- Describe how you would store a social graph in a relational database.
- Describe an efficient algorithm to determine whether or not person X is a 2nd degree connection of person Y.
- Describe an efficient algorithm to determine whether or not person X is a 3rd degree connection of person Y.
- How can you make #3 very quick. E.g. how does Linked In compute 3rd degree connections quickly?
Write a fast implementation for a hash table in Java. You may use arrays and the built in int hashCode() method that returns the hash code for all Java objects.
What is a design pattern and why are they useful in software development?
Write a string to find a substring in a given string. Do this in O(n) or better
Write an iterative function to reverse a string. Do the same thing as a recursive function.
Write a function to implement strstr() i.e. find the first occurrence of one string inside another string.
Write a program to print out a multiplication table, from 1x1 to 12x12. This should look like:
1 2 3 4 5 6 7 8 9 10 11 12 2 4 6 8 10 12 14 16 18 20 22 24 3 6 9 12 15 18 21 24 27 30 33 36 4 8 12 16 20 24 28 32 36 40 44 48 5 10 15 20 25 30 35 40 45 50 55 60 6 12 18 24 30 36 42 48 54 60 66 72 7 14 21 28 35 42 49 56 63 70 77 84 8 16 24 32 40 48 56 64 72 80 88 96 9 18 27 36 45 54 63 72 81 90 99 108 10 20 30 40 50 60 70 80 90 100 110 120 11 22 33 44 55 66 77 88 99 110 121 132 12 24 36 48 60 72 84 96 108 120 132 144
Define the following object oriented concepts:
- Class, object (and the difference between the two)
- Method (as opposed to, say, a C function)
- Static methods and classes
- Multiple inheritance (and give an example)
- Abstract class
- Interface/protocol (and different from abstract class)
- Method overriding
- Method overloading (and difference from overriding)
- Polymorphism (without resorting to examples)
- Method visibility (e.g. public/private/other)
What is a hashtable? Give an example of a type of problem that a hashtable is useful for.
Explain big o notation and how it is useful in computer science to classify algorithms.
- What order is a hash table lookup?
- What order is determining if a number is even or odd?
- What order is finding an item in an unsorted list?
- What order is a binary search?
For the data structures: Array and Linked List explain:
- Where you might use them
- Operations that are commonly supported (add, insert etc)
Describe bitwise operators AND, OR, XOR and NOT. Describe how you might use these.
How do these bitwise operators differ from logical operators?
What's the value of hexadecimal FF in decimal?
Write a program to find the largest integer in an array of integers.
Write a function that sums up integers from a text file that looks like the following:
1 3 27 2 2123
Write function to print the odd numbers from 1 to 99
How many ways can an argument be passed to a method. Explain each method.
What are different types of access modifiers? Explain what they do.
Explain final, finalize() and finally?
Explain what Garbage Collection does. How is it normally initiated? How could you force it to run? What problems can it cause?
Explain the difference between method overloading and method overriding
Explain thedifference between
Name 3 top level class modifiers.
Explain the difference between an inner class and an anonymous class? When would you use these?
Explain what reflection is in Java and give an example of when you might use it.
What is an interface in Java? Give and example of where you might use one. How does this compare to inheritance?
Explain the difference between Integer and int in Java and when you would choose to use one over the other.
Can an inner class be defined inside a method? What variables can be accessed by that class?
Write a program to open a file for reading and print out its entire contents
Write a function to take the following list and return one list of odd numbers and one list of even numbers:
ints = [1,21,53,84,50,66,7,38,9]
A user types the following URL into their browser:
Explain in detail how this would cause a page to appear in their browser, with images, interactive elements (Ajax), styled paragraphs of text etc.
Explain the difference between a mutex and a semaphore? If you need to protect access to an increment operation which one would be the best choice?
If you have access to a function that returns a random integer from one to five, write another function which returns a random integer from one to seven.
Discuss an algorithm to traverse a tree, depth first.
Describe a schema (or classes) to power an online car rental system. Describe the tables and the relationships beween the tables.
Construct a regular expression that matches a valid email address.
Implement a function with signature find_chars(string1, string2) that takes two strings and returns a string that contains only the characters found in string1 and string two in the order that they are found in string1. Implement a version of order N*N and one of order N.
Explain what a deadlock is in multithreaded programming
Given a circular list of integers (when you reach the end of the list you come back to the beginning), what is the most efficient algorithm to find the smallest integer in the list?
circular_list = [22, 52, 66, 82, 5, 8, 12, 19].
Explain the terms static, final, and const
Given a N by N matrix of both negative and positive integers. Write an efficient algorithm to find the sub-matrix with the largest sum of all the contained elements.
Implement a function to divide two integers without using the divide operator.
Design a system to efficiently calculate the top 1MM Google search queries and create a report of these. Additionally:
- You are given twelve servers
- Each has two processors, 4GB of ram and four 400GB hard drives.
- The machines are networked
- The log data as roughly 100 Billion log lines in it.
- The log data comes in twelve, 320 Gb files.
- Each line of the files has roughly 40 search queries
- You can only use open source software or software that you write.
Given an array A[N] containing N numbers. Crate an array Output[N] where Output[i] is equal to the product of all the elements of A[N] except A[i].
For example Output is the product of A to A[N-1] and Output is the product of A and from A to A[N-1].
Do this without using the division operator. Do it in O(n).
You are given a linked list of integers of length N.
N is very large and you don’t know N.
Write a function to return k completely random numbers from the list.
Do this in O(n).
Hint: Use random function rand() (returns a number between 0 and 1) and irand() (return either 0 or 1) 2.
Write a function to efficiently determine the result of a game of Tic Tac Toe.
The function takes as input the game and the sign (x or o) of the player. The function returns if this player has won the game or not.
Carefully consider both the data structure and the algorithm for your answer.
Efficiently calculate the shortest distance between two Facebook users given an API endpoint that returns all friends of a given user.
Given any integer, efficiently find the next highest integer that uses the same digits.
For example if the number is
15432, you should return
Write a function that takes an integer and returns the smallest number that is greater than the given number which is a palendrome.
For example, if the input was
111 the next palindromic number would be
Write a function that, given a word and a dictionary will efficiently return the minimal edits (character addition or deletion) to get to a word that exists in the dictionary.
Write a function,
tokenize_string(input_string, delimiter_list) that returns a list of strings that are separated by the delimiters.
tokenize_string("How now, Mrs. Brown Cow") returns
['How', 'now', 'Mrs', 'Brown', 'Cow']
Write a function to efficiently determine if a linked list has a cycle in it.
Write a function that takes as input a sorted array and modifies the array to compact it, removing duplicates. Also return the new length of the array.
Notes: The input array might be very large.
- input array =
[1, 3, 7, 7, 8, 9, 9, 9, 10]
- transformed array =
[1, 3, 7, 8, 9, 10]
- size = 6
Given two arrays of strings, A and B.
B contains every element in A, and has one additional member, for example:
* A = ['dog', 'cat', 'monkey] * B = ['cat', 'rat', 'dog', 'monkey']
Write a function to find the extra string in B. Do this in O(n)
Express the following table as a static structure, and write a function,
find_routes(source, destination) that efficiently outputs all possible routes.
Source | Dest ~~~~~~ ~~~~ Seattle | LA LA | Florida LA | Maine Florida | Seattle Seattle | Florida
The solution for
find_routes('Seattle', 'Florida') should be
[Seattle -> Florida, Seattle -> LA -> Florida]
Write a function to efficiently convert a floating point number to a rational number. For example, given
Write a function that takes an unsorted integer array, and returns a three element subset whose sum is zero.
Note: This is a special case of the SUBSET-SUM problem. That problem is NP-complete, but we're only looking for subsets of 3 elements. This can be achieved in polynomial time.
Write a function that takes as input a string, and outputs that same string, with any parentheses in it balanced. Do this using the minimum number of edits.
Write a function that takes an array of integers and returns that array rotated by N positions.
For example, if N=2, given the input array
[1, 2, 3, 4, 5, 6] the function should return
[5, 6, 1, 2, 3, 4]
The least common multiple of a set of integers is the smallest positive integer that is a multiple of all of the integers in the set.
Write a function that takes an array of integers and efficiently calculates and returns the LCM.
Write a function that takes as input a binary tree, and returns the length of the longest path.
For example, in this binary tree:
1 / \ 2 3 / 5
the answer is 2, since the path from vertex 1 to vertex 5 involves two edge traversals.
Write function that takes a binary tree and efficiently returns the Nth smallest element.
For example, if N=4, and the tree looks like:
3 / \ 2 5 / / \ 1 4 6
The function should return 4.
Write a function that takes as input two numbers represented as strings, and returns the product of the numbers of a string.
The numbers can be arbitrarily large.
Given a file of size 1TB, containing only 32 bit integers, describe how you would efficiently sort it. You have only 2GB of memory available.
Write a function that takes a an array of integers, and returns the contiguous subsequence of integers with the largest sum.
Write a function to efficiently find the fifth maximum element in a binary search tree. Try to do this without using significant additional storage.
Explain the terms "coupling" and "Cohesion". Is low coupling and high cohesion desirable? Why?
Model the animal kingdom as a set of classes. Discuss the species, their behavior and properties.
Explain the principles of test drive development.
What is an abstract class and when might you use one?
What is a Final class and where might you use one?
Describe the singleton design pattern and how you might use it in practice.
Describe the MVC design pattern and how you might use it in practice.
Describe the Factory design pattern and how you might use it in practice.
Describe the Observer design pattern and how you might use it in practice.
Describe the Strategy design pattern and how you might use it in practice.
Write a function to return the Nth number of Fibonacci sequence.
Design the schema or the classes to implement a library for building card games with. This library should make it easy to build games like Rummy, Poker, Hearts, Whist etc.
Outline the implementation for two of the most important methods of the