yahoo interview

Design a game with deck of cards.

...

singleton

...

Create maximum unique palindromes from a given string

Already given

How to resolve conflict of hash map

Chaining

DNS resolution

Each web server (and indeed any host connected to the internet) has a unique IP address in textual form, translating it to an IP address (in this case, 207.142.131.248) is a process known as DNS resolution or DNS lookup; here DNS stands for Domain Name Service.

What is the difference between hashtable and hashmap?

Image result for What is the difference between hashtable and hashmap?javarevisited.blogspot.com 1)Hashtable is synchronized whereas hashmap is not. 2)Another difference is that iterator in the HashMap is fail-safe while the enumerator for the Hashtable isn't. If you change the map while iterating, you'll know. 3)HashMap permits null values in it, while Hashtable doesn't.

Arraylist vs linkedlist

LinkedList is fast for adding and deleting elements, but slow to access a specific element. ArrayList is fast for accessing a specific element but can be slow to add to either end, and especially slow to delete in the middle. ArrayList is essentially an array. LinkedList is implemented as a double linked list.

pthread

POSIX Threads, usually referred to as pthreads, is an execution model that exists independently from a language, as well as a parallel execution model. It allows a program to control multiple different flows of work that overlap in time.

What is singleton, and pros and cons of it?

Positives: Lazy instantiation, Static initialization Negative: They deviate from the Single Responsibility Principle, Singleton classes cannot be sub classed.

Pseudo code that makes debugging localized and easier

RDD.transformation() RDD.action() RDD.transformation() RDD.action()

Concise pseudo code that makes debugging localized and easier

RDD.transformation().transformation().action()

If you have a lot of data and want to sort it what would you do

Split the file into chunks of MAX_MEM size, Sort each chunk in memory and store as a separate file, Open all chunks as streams of elements, Merge all streams by selecting the lowest element at each step, Delete the chunks

Concurrency

This allows for parallel execution of the concurrent units, which can significantly improve overall speed of the execution in multi-processor and multi-core systems.

Thread vs process

Threads are used for small tasks, whereas processes are used for more 'heavyweight' tasks - basically the execution of applications. Another difference between a thread and a process is that threads within the same process share the same address space, whereas different processes do not.

Check whether a number is palindrome

Yes

Detect cycle in a linkedlist

Yes

Find the kth largest element in an array

Yes

Finding an element in a rotated sorted array,

Yes

Given a binary search tree and a node in it, find the in-order successor of that node in the BST. Note: If the given node has no in-order successor in the tree, return...

Yes

Longest palindromic substring

Yes

Merge k sorted array

Yes

Merge k sorted lists into one

Yes

Print all the leaves of a binary tree

Yes

Remove duplicates from an array

Yes

Reverse a input string

Yes

Reverse string

Yes

Two number represented by linked list, from most significant to lowest. Add them together and generate a new linked list.

Yes

Wildcard matching

Yes

anagrams

Yes

design LFU cache

Yes

finding the median of an unsorted array

Yes

fizz bizz

Yes

postfix evaluation,

Yes

queues with stacks

Yes

reverse linked list

Yes

reverse words in string

Yes

trees - max sum in path

Yes

permutes a list of numbers, unique permutations

Yes ,

Reverse characters of each word in a sentence

Yes, reverse words in a string III

Using an array of singular animal names, create an RDD that contains a list of animal names singular, and another RDD that contains a one-dimensional list of animal names both singular and plural

animals = ['cat','dog','bird','rat'] animalsRDD = sc.parallelize(animals,4) singularAndPluralAnimalsRDD = animalsRDD.flatMap(lambda x: (x, x + 's'))

Using an array of singular animal names, create an RDD that contains a list of animal names singular, and another pair RDD that contains a two-dimensional list of animal names both singular and plural

animals = ['cat','dog','bird','rat'] animalsRDD = sc.parallelize(animals,4) singularAndPluralAnimalsRDD = animalsRDD.map(lambda x: (x, x + 's'))

Create a range of numbers from 1 .. 10000 using Python

data = xrange(1,10000)

Define a Python function to return a given value - 1, then use the function to transform xrangeRDD into subRDD using the function

define sub(value): return (value - 1) subRDD = xrangeRDD.map(sub)

In a reusable fashion, create a new RDD from xrangeRDD that contains only elements less than 10

define ten(value): if (value<10): return True else: return False filteredRDD = xrangeRDD.filter(ten)

In a non reusable fashion, create a new RDD from xrangeRDD that contains only elements less than 10

filteredRDD = xrangeRDD.filter(lambda x: x < 10)

Find lowest unique minimum

http://stackoverflow.com/questions/11944737/finding-the-minimum-unique-number-in-an-array

To count all log file items with the same timestamp and output the result sorted according to time

http://stackoverflow.com/questions/7347054/sort-logfile-by-timestamp-on-linux-command-line

Reverse a BST into a Binary tree and linked list

http://www.geeksforgeeks.org/convert-bst-to-a-binary-tree/

Find a target value in a binary tree recursively and iteratively

http://www.geeksforgeeks.org/find-closest-element-binary-search-tree/

Find path in a directed graph

http://www.geeksforgeeks.org/find-if-there-is-a-path-between-two-vertices-in-a-given-graph/

How can you find the greatest possible product of multiplying three numbers in a list

http://www.geeksforgeeks.org/find-maximum-product-of-a-triplet-in-array/

Find first non-repeated character

http://www.geeksforgeeks.org/given-a-string-find-its-first-non-repeating-character/

Convert a BST into Doubly Linked List

http://www.geeksforgeeks.org/in-place-convert-a-given-binary-tree-to-doubly-linked-list/

Given a line, print pascals triangle

http://www.geeksforgeeks.org/pascal-triangle/

Reverse a stack

http://www.geeksforgeeks.org/reverse-a-stack-using-recursion/

Write an algorithm to calculate x to the power of n in less than O(n) time

http://www.geeksforgeeks.org/write-a-c-program-to-calculate-powxn/

Binary Tree Question: Compare two binary tree and return if they are the same or not.

http://www.geeksforgeeks.org/write-c-code-to-determine-if-two-trees-are-identical/

design concurrent load balancer,

http://www.javaperformancetuning.com/tips/loadbalance.shtml

Find the longest string containing common substring in a string

https://en.wikibooks.org/wiki/Algorithm_Implementation/Strings/Longest_common_substring#Python_2

Print the items in wordsRDD by partition, including the index, joining items in each partition by a comma

itemsByPartRDD = wordsRDD.mapPartitionsWithInde(lambda index, iterator: [(index, list(iterator))])

Print the items in wordsRDD by partition, joining items in each partition by a comma

itemsRDD= wordsRDD.mapPartitions(lambda iterator: [','.join(iterator)]) print itemsRDD.collect()

Show the current location of filteredRDD (memory, disk, etc.)

print filteredRDD.getStorageLevel()

Print all elements (in all partitions) of subRDD

print subRDD.collect()

Print the global count of elements across all partitions of subRDD

print subRDD.count()

Print new RDD that shows the count of each element in xrangeRDD

print xrangeRDD.countByValue()

Print the first element of xrangeRDD

print xrangeRDD.first()

Print the sum of all elements in xrangeRDD using Python's add function

print xrangeRDD.reduce(add)

Print the sum of all elements in xrangeRDD using an inline function

print xrangeRDD.reduce(lambda a,b: a + b)

Print the first three elements of xrangeRDD

print xrangeRDD.take(3)

Print the smallest three elements in xrangeRDD

print xrangeRDD.takeOrdered(3)

Print ten random elements in xrangeRDD, duplicates prohibited

print xrangeRDD.takeSample(withReplacement=False, num=10)

Print ten random elements in xrangeRDD, duplicates are OK

print xrangeRDD.takeSample(withReplacement=True, num=10)

Print eight random elements in xrangeRDD, duplicates OK, deterministically (multiple invocations produce same result)

print xrangeRDD.takeSample(withReplacement=True, num=8, seed=500)

Print the largest three elements in xrangeRDD

print xrangeRDD.top(3)

Check if the string is balanced. eg {{}} should return true,

valid parantheses

Parse a string with spaces

word split, Yes

Place wordsRDD in memory to improve response times involving this RDD

wordsRDD.cache()

Remove wordsRDD from memory

wordsRDD.unpersist()

Create an RDD with 8 partitions given the variable data

xrangeRDD = sc.parallelize(data,8)

Show the number of partitions for xrangeRDD

xrangeRDD.getNumPartitions()

Set the name of xrangeRDD to MyRDD

xrangeRDD.setName('MyRDD')

Print the lineage (set of transformation) of xrangeRDD

xrangeRDD.toDebugString()