An algorithm is a sequence of unambiguous steps to do a task. The challenges below require you to come up with algorithms to solve the problems.

Array
String
Dictionary
Dynamic Programming
Recursion
Tree

Number of Steps to Reduce a Number to Zero
Power of Three
Add Digits
Happy Number
Last Stone Weight
Count and Say
Pow(x, n)
K-th Symbol in Grammar
Jump Game
Keys and Rooms
Number of Islands
Number of Provinces
Word Search
Time Needed to Inform All Employees
Subsets
Combinations
Rotting Oranges
Target Sum
Letter Combinations of a Phone Number
Permutations
Perfect Squares
Maximal Square
Open the Lock
Generate Parentheses