## Sunday, September 30, 2012

### A great machine learning book

Many times people are asking  what is the best book to start studying machine learning. Among other books, I'd like to suggest: Machine Learning, An algorithmic Perspective, which has a good mix of topics covered and where every algorithm is implemented in python

## Saturday, September 29, 2012

### Exit a labyrinth

given a matrix of 0/1, where the 1s represent the walls of a labyrinth, find the exit

## Friday, September 28, 2012

Gift could be a changing moment for Facebook. In my view, this is a service with a great user experience and it also has opportunities for increasing FB's revenues. In my view, Facebook can become a cash-cow but they need to add services for allowing money transfer or gift transfers ( see my posting on this topic of about 1 year ago "http://codingplayground.blogspot.co.uk/2011/09/facebook-social-wallet.html )

## Tuesday, September 25, 2012

### Given a tree, return an array A

where A[i] is the head of a linked list containing all the elements at level i.

## Sunday, September 23, 2012

### Convert a BST into a double linked list

preserving the order

## Saturday, September 22, 2012

### K-Means: describe the intuition behind the algo

and write some code for it

## Friday, September 21, 2012

### SVM

Explain the intuition behind SVM and optionally try to figure out the math

## Tuesday, September 18, 2012

### Select friends from your social network

You need to select the maximum number of friends in your network and invite them to a party. The requirement is that each friend knows a minimum of 5 friends and she does not know at least 5 other friends.

## Saturday, September 15, 2012

### Given an array of integers A, compute efficiently the max in any interval [i, j]

Compare time and space

## Thursday, September 13, 2012

### Unsorted array

Given an unsorted array, how to divide them into two equal arrays whose difference of sum is minimum

## Wednesday, September 12, 2012

### Sort a large set of std::vector

Sort a large set of std::vector, larger than the size of RAM

## Tuesday, September 11, 2012

### Array rotation

Given an array, rotate the elements of an array within O(n) time and with 0(1) space

## Monday, September 10, 2012

### A frog jumping

A frog can jump a river of n meters and at each step she can jump either x-1 or x or x+1 meter if she jumped x meter at the previous step. She can jump just if the starting place and the ending place has a stone. The available stones are maintained in an array S[i] given as input. The first just is just 1 meter. Can you compute whether or not the frog will arrive at the destination?

## Sunday, September 9, 2012

### implement a first fit strategy

You have a m set of boxes of different sizes and a set of n envelopes. Find a strategy to fit the box in the envelopes

## Thursday, September 6, 2012

### an url can contain words

an url can contain words. For instance akillernewappforwork.com. Device an algorithm for extracting all the words from an url

## Wednesday, September 5, 2012

### Longest subsequence

Given an array A of integers such that #A = n, find the longest sequence such that i_j < i_{j+1} and A[i_j] <= A[i_{j+1}] for any j \in [1, k-1]

## Tuesday, September 4, 2012

### Max sum in an array

Given an array of integers A find a, b such that \sum_{i=a}^b A[i] is maximized

## Sunday, September 2, 2012

### Search engines and monetization

Search engines are making money selling ads. Can you envision any different strategy?

## Saturday, September 1, 2012

### inverted lists

Given a very large set of document, you can define the following relation d_i ->; w_a, w_b, w_c, ...... meaning that the document d_i contains the word w_a, w_b, w_c, and so on and so forth

Suppose you want to invert the relation and build lists such as

w_a -> d_i, d_j, d_k ...

meaning that the word w_a is contained in documents  d_i, d_j, d_k ...

how would you proceeed?