String Expansion
You are given a string s consisting of lowercase alphabet characters, digits, and brackets"(" and ")". s encodes a longer string and is represented as concat...
Posts with tag 'recursion'
IP Address Combinations
Given a string of digits ip, generate all possible valid IP address combinations and return them in sorted order.
Phone Number Combinations
Given a string digits containing 2 to 9 inclusive, return in sorted lexicographic order all possible strings it could represent when mapping to letters on a ...
Upside Down Numbers
An upside down number is one that appears the same when flipped 180 degrees. Given n, return all upside down numbers as strings whose length is n, sorted in ...