# TypeScript

One of the easiest ways to add new exercises to the TypeScript track is to translate them from other language tracks on Exercism. This page lists all of the problem specifications in the common pool of exercises which have not yet been implemented in TypeScript.

The icon links to the language-independent description of the problem.

The icon links to the canonical test data.

We also link to all the implementations of each exercise in other languages, which you can use for inspiration.

Once you've picked an exercise, follow the instructions in this guide and submit your pull request to the TypeScript track repository on GitHub.

### Atbash Cipher

Create an implementation of the atbash cipher, an ancient encryption system created in the Middle East.

### Nucleotide Count

Given a DNA string, compute how many times each nucleotide occurs in the string.

### Roman Numerals

Write a function to convert from normal numbers to Roman Numerals.

### Triangle

Determine if a triangle is equilateral, isosceles, or scalene.

### Allergies

Given a person's allergy score, determine whether or not they're allergic to a given item, and their full list of allergies.

### Grains

Calculate the number of grains of wheat on a chessboard given that the number on each square doubles.

### Largest Series Product

Given a string of digits, calculate the largest product for a contiguous substring of digits of length n.

### Sum Of Multiples

Given a number, find the sum of all the multiples of particular numbers up to but not including that number.

### Luhn

Given a number determine whether or not it is valid per the Luhn formula.

### Clock

Implement a clock that handles times without dates.

### Pascals Triangle

Compute Pascal's triangle up to a given number of rows.

### Sieve

Use the Sieve of Eratosthenes to find all the primes from 2 up to a given number.

### Nth Prime

Given a number n, determine what the nth prime is.

Convert a number, represented as a sequence of digits in one base, to any other base.

### Isogram

Determine if a word or phrase is an isogram.

### Meetup

Calculate the date of meetups.

### Bracket Push

Make sure the brackets and braces all match.

### Perfect Numbers

Determine if a number is perfect, abundant, or deficient based on Nicomachus' (60 - 120 CE) classification scheme for natural numbers.

### Prime Factors

Compute the prime factors of a given natural number.

### Crypto Square

Implement the classic method for composing secret messages called a square code.

### Robot Simulator

Write a robot simulator.

### Series

Given a string of digits, output all the contiguous substrings of length `n` in that string.

### Accumulate

Implement the `accumulate` operation, which, given a collection and an operation to perform on each element of the collection, returns a new collection containing the result of applying that operation to each element of the input collection.

### Binary Search

Implement a binary search algorithm.

### Minesweeper

Add the numbers to a minesweeper board

### Secret Handshake

Given a decimal number, convert it to the appropriate sequence of events for a secret handshake.

### Pig Latin

Implement a program that translates from English to Pig Latin

### Queen Attack

Given the position of two queens on a chess board, indicate whether or not they are positioned so that they can attack each other.

### Flatten Array

Take a nested list and return a single list with all values except nil/null

### List Ops

Implement basic list operations

### Run Length Encoding

Implement run-length encoding and decoding.

### Sublist

Write a function to determine if a list is a sublist of another list.

### Binary Search Tree

Insert and search for numbers in a binary tree.

### Custom Set

Create a custom set type.

### Ocr Numbers

Given a 3 x 4 grid of pipes, underscores, and spaces, determine which number is represented, or whether it is garbled.

### Palindrome Products

Detect palindrome products in a given range.

Detect saddle points in a matrix.

### Strain

Implement the `keep` and `discard` operation on collections. Given a collection and a predicate on the collection's elements, `keep` returns a new collection containing those elements where the predicate is true, while `discard` returns a new collection containing those elements where the predicate is false.

### Bowling

Score a bowling game

### Change

Correctly determine change to be given using the least number of coins

### Kindergarten Garden

Given a diagram, determine which plants each child in the kindergarten class is responsible for.

### Pythagorean Triplet

There exists exactly one Pythagorean triplet for which a + b + c = 1000. Find the product a * b * c.

### Circular Buffer

A data structure that uses a single, fixed-size buffer as if it were connected end-to-end.

### Collatz Conjecture

Calculate the number of steps to reach 1 using the Collatz conjecture

### Matrix

Given a string representing a matrix of numbers, return the rows and columns of that matrix.

### Simple Cipher

Implement a simple shift cipher like Caesar and a more secure substitution cipher

### Bank Account

Simulate a bank account supporting opening/closing, withdraws, and deposits of money. Watch out for concurrent transactions!

### Diamond

Given a letter, print a diamond starting with 'A' with the supplied letter at the widest point.

### Rotational Cipher

Create an implementation of the rotational cipher, also sometimes called the Caesar cipher.

### Forth

Implement an evaluator for a very simple subset of Forth

### House

Output the nursery rhyme 'This is the House that Jack Built'.

### React

Implement a basic reactive system.

Write a simple linked list implementation that uses Elements and a List

### Alphametics

Write a function to solve alphametics puzzles.

### Connect

Compute the result for a game of Hex / Polygon

### Poker

Pick the best hand(s) from a list of poker hands.

### Tournament

Tally the results of a small football competition.

### Transpose

Take input text and output it transposed.

### Twelve Days

Output the lyrics to 'The Twelve Days of Christmas'

### Two Fer

Create a sentence of the form "One for X, one for me."

### Dominoes

Make a chain of dominoes.

### Parallel Letter Frequency

Count the frequency of letters in texts using parallel computation.

### Protein Translation

Translate RNA sequences into proteins.

### Variable Length Quantity

Implement variable length quantity encoding and decoding.

### Book Store

To try and encourage more sales of different books from a popular 5 book series, a bookshop has decided to offer discounts of multiple-book purchases.

### Proverb

For want of a horseshoe nail, a kingdom was lost, or so the saying goes. Output the full text of this proverbial rhyme.

### Rail Fence Cipher

Implement encoding and decoding for the rail fence cipher.

### Zipper

Creating a zipper for a binary tree.

### Pov

Reparent a graph on a selected node

### Rectangles

Count the rectangles in an ASCII diagram.

### Spiral Matrix

Given the size, return a square matrix of numbers in spiral order.

### Word Search

Create a program to solve a word search puzzle.

### Complex Numbers

Implement complex numbers.

### Diffie Hellman

Diffie-Hellman key exchange.

### Grep

Search a file for lines matching a regular expression pattern. Return the line number and contents of each matching line.

### Scale Generator

Generate musical scales, given a starting note and a set of intervals.

### Two Bucket

Given two buckets of different size, demonstrate how to measure an exact number of liters.

### Zebra Puzzle

Solve the zebra puzzle.

### Error Handling

Implement various kinds of error handling and resource management

### Markdown

Refactor a Markdown parser

### Sgf Parsing

Parsing a Smart Game Format string.

### Dot Dsl

Write a Domain Specific Language similar to the Graphviz dot language

### Go Counting

Count the scored points on a Go board.

### Hangman

Implement the logic of the hangman game using functional reactive programming.

### Ledger

Refactor a ledger printer.

### Lens Person

Use lenses to update nested records (specific to languages with immutable data).

### Tree Building

Refactor a tree building algorithm.

### Paasio

Report network IO statistics