Breaking Trello challenge

instructions.md

Write JavaScript (or CoffeeScript) code to find a 9 letter string of characters that contains only letters from

acdegilmnoprstuw

such that the hash(the_string) is

956446786872726

if hash is defined by the following pseudo-code:

Int64 hash (String s) {
    Int64 h = 7
    String letters = "acdegilmnoprstuw"
    for(Int32 i = 0; i < s.length; i++) {
        h = (h * 37 + letters.indexOf(s[i]))
    }
    return h
}

For example, if we were trying to find the 7 letter string where hash(the_string) was 680131659347, the answer would be "leepadg".

solution.js

//Same solution in JavaScript

(function() {
  var solve = function(base, set, hash, code){
    return [Math.floor(hash/base), set[hash%base] + code]
  };
  var solvePuzzle = solve.bind(null, 37, "acdegilmnoprstuw");
  var puzzle = [956446786872726, ''], iterations = 9;
  while(iterations--)
    puzzle = solvePuzzle.apply(null, puzzle);
  console.log(puzzle);
})();

solution.lhs

Every number returned by the `hash` function is given by the sum
of a number `x` where `mod x 37 == 0` and a number `x <- [0..15]`
 
The `solve` function calculates the next number to solve
and add the current letter to the solution
 
> solve base set (hash, code) = (div hash base, set !! mod hash base : code)
 
The `solvePuzzle` function defines the parameter of the puzzle
 
> solvePuzzle = solve 37 "acdegilmnoprstuw"
 
The `main` function iterates on `solve` 9 times with hash as the starting value
 
> main = print (iterate solvePuzzle (956446786872726, "") !! 9)

Adding an extra Haskell solution because, at 3LOC is pretty damn expressive and concise