Solutions to timed coding challenges on Code Fights
Given an encoded string, return its corresponding decoded string.
The encoding rule is: k[encoded_string], where the encoded_string inside the square brackets is repeated exactly k times. Note: k is guaranteed to be a positive integer.
Note that your solution should have linear complexity because this is what you will be asked during an interview.
Ticket numbers usually consist of an even number of digits. A ticket number is considered lucky if the sum of the first half of the digits is equal to the sum of the second half.
Given a ticket number n, determine if it's lucky or not.
Note: Write a solution that only iterates over the string once and uses O(1) additional memory, since this is what you would be asked to do during a real interview.
Given a string s, find and return the first instance of a non-repeating character in it. If there is no such character, return '_'.
Given an array a that contains only numbers in the range from 1 to a.length, find the first duplicate number for which the second occurrence has the minimal index. In other words, if there are more than 1 duplicated numbers, return the number for which the second occurrence has a smaller index than the second occurrence of the other number does. If there are no such elements, return -1.
Given the string, check if it is a palindrome
Boggle is a popular word game in which players attempt to find words in sequences of adjacent letters on a rectangular board.
Given a two-dimensional array board that represents the character cells of the Boggle board and an array of unique strings words, find all the possible words from words that can be formed on the board.
Note that in Boggle when you're finding a word, you can move from a cell to any of its 8 neighbors, but you can't use the same cell twice in one word.
Note: Try to solve this task in-place (with O(1) additional memory), since this is what you'll be asked to do during an interview.
You are given an n x n 2D matrix that represents an image. Rotate the image by 90 degrees (clockwise).