Find the peak 3n+1 sequence value
A Collatz sequence is the sequence where, for a given number n, the next number in the sequence is either n/2 if the number is e...

Kaprekar Steps
6174 is the <http://en.wikipedia.org/wiki/6174_%28number%29 Kaprekar constant>. All natural numbers less than 10,000 (except som...

Find the two-word state names
Given a list of states, remove all the states that have two-word names. If s1 = 'Alabama Montana North Carolina Vermont N...

Word Counting and Indexing
You are given a list of strings, each being a list of words divided by spaces. Break the strings into words, then return a maste...

The Goldbach Conjecture, Part 2
The <http://en.wikipedia.org/wiki/Goldbach's_conjecture Goldbach conjecture> asserts that every even integer greater than 2 can ...

Encode Roman Numerals
Create a function taking a non-negative integer as its parameter and returning a string containing the Roman Numeral representat...

Elapsed Time
Given two date strings d1 and d2 of the form yyyy/mm/dd HH:MM:SS (assume hours HH is in 24 hour mode), determine how much time, ...

Find state names that end with the letter A
Given a list of US states, remove all the states that end with the letter A. Example: Input s1 = 'Alabama Montana Nebras...

The Goldbach Conjecture
The <http://en.wikipedia.org/wiki/Goldbach's_conjecture Goldbach conjecture> asserts that every even integer greater than 2 can ...

Pattern matching
Given a matrix, m-by-n, find all the rows that have the same "increase, decrease, or stay same" pattern going across the columns...

Tic Tac Toe FTW
Given a tic tac toe board: * 1 represents X * 0 represents empty. * -1 represents O It is X's move. If there is an imme...

Summing Digits within Text
Given a string with text and digits, add all the numbers together. Examples: Input str = '4 and 20 blackbirds baked in a...

Scrabble Scores
Given a word, determine its score in <http://en.wikipedia.org/wiki/Scrabble Scrabble>. The input string will always be provi...

Counting Sequence
Given a vector x, find the "counting sequence" y. A counting sequence is formed by "counting" the entries in a given sequence...

Maximum running product for a string of numbers
Given a string s representing a list of numbers, find the five consecutive numbers that multiply to form the largest number. Spe...

Duplicates
Write a function that accepts a cell array of strings and returns another cell array of strings *with only the duplicates* retai...

What is the next step in Conway's Life?
Given a matrix A that represents the state of <http://en.wikipedia.org/wiki/Conway's_Game_of_Life Conway's game of Life> at one ...

QWERTY coordinates
Given a lowercase letter or a digit as input, return the row where that letter appears on a <http://en.wikipedia.org/wiki/Keyboa...

Sums with Excluded Digits
Add all the integers from 1 to n in which the digit m does not appear. m will always be a single digit integer from 0 to 9. no...

Making change
Given an amount of currency, return a vector of this form: [100 50 20 10 5 2 1 0.5 0.25 0.1 0.05 0.01] Example: Input a = ...

<http://en.wikipedia.org/wiki/Benford%27s_law Benford's Law> states that the distribution of leading digits is not random. This...

Which doors are open?
There are n doors in an alley. Initially they are all shut. You have been tasked to go down the alley n times, and open/shut the...

Make a Palindrome Number
Some numbers like 323 are palindromes. Other numbers like 124 are not. But look what happens when we add that number to a revers...

Trimming Spaces
Given a string, remove all leading and trailing spaces (where space is defined as ASCII 32). Input a = ' singular value deco...

Find the palindrome
Given the string a, find the longest palindromic sub-string b. So when a = 'xkayakyy'; you should return b = 'kayak';

Subset Sum
Given a vector v of integers and an integer n, return the the indices of v (as a row vector in ascending order) that sum to n. I...

Find the alphabetic word product
If the input string s is a word like 'hello', then the output word product p is a number based on the correspondence a=1, b=2, ....

Cell joiner
You are given a cell array of strings and a string delimiter. You need to produce one string which is composed of each string fr...

Reverse Run-Length Encoder
Given a "counting sequence" vector x, construct the original sequence y. A counting sequence is formed by "counting" the entrie...

Which values occur exactly three times?
Return a list of all values (sorted smallest to largest) that appear exactly three times in the input vector x. So if x = [1 2...