5kyu_CodingWithSquaredStrings.js

// 5kyu - Coding with Squared Strings

// A squared string has n lines, each substring being n characters long: For example:

// s = "abcd\nefgh\nijkl\nmnop" is a squared string of size 4.

// We will use squared strings to code and decode texts. To make things easier we suppose that our original text doesn't include the character '\n'.

// Coding
// Input:

// a text t of length l.
// Consider the smallest integer n such that n * n be greater or equal to l.
// Complete t with the char of ascii code 11 (we suppose that this char is not in our original text) until the length of t is n * n.
// From now on we can transform the new t in a squared string s of size n by inserting '\n' where needed.
// Apply a clockwise rotation of 90 degrees to s: that's it for the coding part.
// Decoding
// Input:

// a squared string s resulting from the coding
// Apply a counter-clockwise rotation of 90 degrees to s
// Do some cleaning to have the original text t
// You can see clockwise rotation of 90 degrees: http://www.codewars.com/kata/56dbeec613c2f63be4000be6 You can see counter-clockwise rotation of 90 degrees: http://www.codewars.com/kata/56dbf59b0a10feb08c000227

// Example:
// t = "I.was.going.fishing.that.morning.at.ten.o'clock"

// code(t) -> "c.nhsoI\nltiahi.\noentinw\ncng.nga\nk..mg.s\n\voao.f.\n\v'trtig"

// decode(code(t)) == "I.was.going.fishing.that.morning.at.ten.o'clock"

// (Dots indicate spaces since they are quite invisible).

// Notes:
// Swift : character 11 is replaced by "\u{F7}" (ie "÷" - alt 246 -)
// Ocaml : character 11 is replaced by '&'
// Perl : character 11 is replaced by '&'
// Fortran: Your returned string for both functions are not permitted to contain redundant leading/trailing whitespace. In return, you may safely assume that all input strings passed into your function(s) will not contain redundant leading/trailing whitespace, i.e. you do not and should not trim the input string before operating on it

// Don't use this coding to keep your secrets:-)

function code(s) {
  let str = s.replace(/\n/g, ''), len = str.length, res = '', n = Math.ceil(Math.sqrt(len)), m = n * (n - 1);
  for (var i = 0; i < n; i++) {
    res += "\n";
    for (var j = 0; j < n; j++)
      res += str[m + i - n * j] || "\v";
  }
  return res.slice(1);
}

function decode(s) {
  let res = code(code(code(s)));
  return res.replace(/(\n|\v)/g, '');
}