  Prepare for Hack ReactorThe premiere coding bootcamp in California

Course Material

View all Bootcamp courses
Next Bootcamp course
• Practice Challenges
• First Reverse

For this challenge you will be reversing a string. 201609 solutions

• First Factorial

For this challenge you will be determining the factorial for a given number. 184562 solutions

• Longest Word

For this challenge you will be determining the largest word in a string. 126683 solutions

• Letter Changes

For this challenge you will be manipulating characters in a string based off their positions in the alphabet. 125207 solutions

For this challenge you will be adding up all the numbers from 1 to a certain argument. 99802 solutions

• Letter Capitalize

For this challenge you will be capitalizing certain characters in a string. 82706 solutions

• Simple Symbols

For this challenge you will be determining whether or not certain characters are in correct positions. 68104 solutions

• Check Nums

For this challenge you will be comparing two numbers and determining which one is greater. 69701 solutions

• Time Convert

For this challenge you will be determining the difference in hours and minutes between two given times. 56793 solutions

• Alphabet Soup

For this challenge you will be sorting characters in a string. 50380 solutions

• AB Check

For this challenge you will determine if two characters are separated a specific way in the string. 19619 solutions

• Vowel Count

For this challenge you will be counting all the vowels in a string. 19005 solutions

• Word Count

For this challenge you will be determining how many words a sentence contains. 17785 solutions

• Ex Oh

For this challenge you will traverse a string and determine if there is an equal amount of certain characters. 17044 solutions

• Palindrome

For this challenge you will determine if a string is written the same way forward and backwards. 22914 solutions

• Arith Geo

For this challenge you will determine if numbers within an array follow an arithmetic or geometric sequence. 15563 solutions

For this challenge you will determine if numbers in an array can add up to a certain number in the array. 10895 solutions

• Letter Count I

For this challenge you will determine which word has the greatest number of repeated letters. 9585 solutions

• Second GreatLow

For this challenge you will determine the second lowest and greatest numbers in an array. 15635 solutions

• Division Stringified

For this challenge you will divide two numbers and return them in a certain format. 11183 solutions

• Counting Minutes I

For this challenge you will return the total number of minutes between two times. 6717 solutions

• Mean Mode

For this challenge you will determine if the mode equals the mean in an array. 8839 solutions

• Dash Insert

For this challenge you will be manipulating a string using dashes (-). 10089 solutions

• Swap Case

For this challenge you will be swapping the case of each character in the string. 9636 solutions

For this challenge you will traverse a string searching for all the numbers and then you will add them up. 9175 solutions

• Third Greatest

For this challenge you will determine the third largest string within an array. 9376 solutions

• Powers of Two

For this challenge you will be determining whether or not a number is a power of two. 9942 solutions

For this challenge you will be determining the additive persistence for a given number. 6912 solutions

• Multiplicative Persistence

For this challenge you will be determining the multiplicative persistence for a given number. 5598 solutions

• Off Line Minimum

For this challenge you will be creating a subset of an array. 7261 solutions

• Changing Sequence

For this challenge you will determine when an array changes sequences. 4321 solutions

• Overlapping Ranges

For this practice test you will determine the intersection between two sets. 3858 solutions

• Superincreasing

For this challenge you will determine if each number is greater than the sum of all previous elements in an array. 3593 solutions

• Hamming Distance

For this challenge you will determine the difference between two strings. 2964 solutions

• Rectangle Area

For this challenge you will determine the area of a rectangle. 3617 solutions

• Bitwise One

For this challenge you will perform a bitwise operation on two binary numbers. 2651 solutions

• Other Products

For this challenge you will return the product of a set of elements in an array. 2622 solutions

• Wave Sorting

For this challenge you will determine if numbers in an array can be sorted in a particular way. 3286 solutions

• Array Matching

For this challenge you will add elements from two arrays in a particular order. 2934 solutions

• Binary Reversal

For this challenge you will be reversing a binary string. 5312 solutions

• Next Palindrome

For this challenge you will be determining the next largest palindrome. 1859 solutions

• Largest Pair

For this challenge you will determine the largest double digit number. 2159 solutions

• Nonrepeating Character

For this challenge you will find the first non-repeating character in a string. 7219 solutions

• Two Sum

For this challenge you will determine if two elements can sum to some larger number. 5630 solutions

• Bitwise Two

For this challenge you will perform a bitwise operation on two binary numbers. 1495 solutions

• Power Set Count

For this challenge you will determine the length of a power set. 1706 solutions

• Product Digits

For this challenge you will be determining the least amount of digits needed to produce a number. 2035 solutions

• Palindrome Creator

For this challenge you will be determining if you can create a palindrome from a list of numbers. 3931 solutions

• Basic Roman Numerals

For this challenge you will be converting a string of Roman numerals. 1485 solutions

• Food Distribution

For this challenge you will determine how to optimally distribute food to people. 1427 solutions

• Three Sum

For this challenge you will determine if three elements can sum to some larger number. 1809 solutions

• Correct Path

For this challenge you will be traversing a matrix searching for the correct path to take. 4121 solutions

• Scale Balancing

For this challenge you will be balancing a scale with weights on it. 5933 solutions

• Three Numbers

For this challenge you will be searching for a set of numbers in a string. 1276 solutions

• Alphabet Searching

For this challenge you will determine if a set of characters exists in a string. 1244 solutions

• Time Difference

For this challenge you will be searching for the smallest time difference. 2173 solutions

• Triangle Row

For this challenge you will be adding up a whole row from Pascal's triangle. 749 solutions

• Vowel Square

For this challenge you will determine if a square of vowels exists in a matrix. 3596 solutions

• Closest Enemy

For this challenge you will search in an array for an enemy. 2901 solutions

• Closest Enemy II

For this challenge you will search in a matrix for an enemy. 3604 solutions

• Number Stream

For this challenge you will determine if a stream of digits occurs in a string. 3441 solutions

• Largest Four

For this challenge you will need to find the four largest elements in an array. 3136 solutions

• Distinct Characters

For this challenge you will determine if a string contains some number of distinct characters. 996 solutions

• Questions Marks

For this challenge you will be determining if a string follows a particular pattern. 18173 solutions

• Camel Case

For this challenge you will be converting a string into camel case format. 4978 solutions

• ASCII Conversion

For this challenge you will be replacing certain characters in a string. 1038 solutions

• Simple Evens

For this challenge you will be checking whether a number is even. 985 solutions

• Snake Case

For this challenge you will be converting a string into snake case format. 2084 solutions

• Find Intersection

For this challenge you will be manipulating an array. 17735 solutions

• Sum Multiplier

For this challenge you will determine if two numbers can be multiplied to some specific number. 5210 solutions

• String Merge

For this challenge you will be merging two different strings together. 1070 solutions

• One Decremented

For this challenge you will be counting how many times a specific pattern occurs in a large number. 986 solutions

• Element Merger

For this challenge you will be combining all of the elements in an array into a single number. 952 solutions

• GCF

For this challenge you will determine the greatest common factor of two numbers. 861 solutions

• Serial Number

For this challenge you will be determining if a string produces a valid serial number. 1894 solutions

• String Periods

For this challenge you will need to find the smallest repeating substring. 2946 solutions

• Palindrome Swapper

For this challenge you will determine if a palindrome can be created in a string. 933 solutions

• Remove Brackets

For this challenge you will determine how to create evenly matched brackets. 3885 solutions

• Command Line

For this challenge you will be parsing a command line string and counting its characters. 588 solutions

• Star Rating

For this challenge you will be calculating how to display a 5 star rating. 4128 solutions

• Moving Median

For this challenge you will calculate the median in an array within a sliding window. 2560 solutions

• Group Totals

For this challenge you will be adding values from key, value pairs. 3717 solutions

• String Changes

For this challenge you will manipulate a string based on two rules. 659 solutions

• FizzBuzz

For this challenge you will be solving the classic Fizz Buzz problem. 5369 solutions

• H Distance

For this challenge you will determine the difference between two strings. 1094 solutions

• Different Cases

For this challenge you will be converting a string into camel case format. 581 solutions

• Equivalent Keypresses

For this challenge you will be manipulating an array. 987 solutions 3179 solutions