5.6 KiB

Raw Blame History

id	title	challengeType	forumTopicId	dashedName
5a23c84252665b21eecc8029	ストラドリングチェッカーボード	1	302325	straddling-checkerboard

--description--

Implement functions to encrypt and decrypt a message using the straddling checkerboard method.

Each function will take two arguments, a message string and an alphabet array. The alphabet array will contain 3 strings representing the 3 rows of the straddling checkerboard.

The output of the straddle() function should be a series of decimal digits. Numbers should be encrypted by inserting the escape character before each digit, then including the digit unencrypted.

This should be reversed for decryption with the unstraddle() function.

--hints--

straddle should be a function.

assert(typeof straddle == 'function');

straddle("One night-it was on the twentieth of March, 1888-I was returning.",["ESTONIA R", "BCDFGHJKLM", "PQUVWXYZ./"]) should return a string.

assert(
  typeof straddle(
    'One night-it was on the twentieth of March, 1888-I was returning.',
    ['ESTONIA  R', 'BCDFGHJKLM', 'PQUVWXYZ./']
  ) == 'string'
);

straddle("One night-it was on the twentieth of March, 1888-I was returning.",["ESTONIA R", "BCDFGHJKLM", "PQUVWXYZ./"]) should return "34045747525284613427502840425027537379697175891898898898584619028294547488".

assert.equal(
  straddle(
    'One night-it was on the twentieth of March, 1888-I was returning.',
    ['ESTONIA  R', 'BCDFGHJKLM', 'PQUVWXYZ./']
  ),
  '34045747525284613427502840425027537379697175891898898898584619028294547488'
);

straddle("One night-it was on the twentieth of March, 1888-I was returning",["HOL MES RT", "ABCDFGIJKN", "PQUVWXYZ./"]) should return "139539363509369743061399059745399365901344308320791798798798367430685972839363935".

assert.equal(
  straddle('One night-it was on the twentieth of March, 1888-I was returning', [
    'HOL MES RT',
    'ABCDFGIJKN',
    'PQUVWXYZ./'
  ]),
  '139539363509369743061399059745399365901344308320791798798798367430685972839363935'
);

straddle("Thecheckerboardcakerecipespecifies3largeeggsand2.25cupsofflour.",["ET AON RIS", "BCDFGHJKLM", "PQ/UVWXYZ."]) should return "125021250212707204372221327070218600960021823809623283724002424935226226962262521636094232328463769".

assert.equal(
  straddle('Thecheckerboardcakerecipespecifies3largeeggsand2.25cupsofflour.', [
    'ET AON RIS',
    'BCDFGHJKLM',
    'PQ/UVWXYZ.'
  ]),
  '125021250212707204372221327070218600960021823809623283724002424935226226962262521636094232328463769'
);

unstraddle should be a function.

assert(typeof unstraddle == 'function');

unstraddle("34045747525284613427502840425027537379697175891898898898584619028294547488",["ESTONIA R", "BCDFGHJKLM", "PQUVWXYZ./"]) should return a string.

assert(
  typeof unstraddle(
    '34045747525284613427502840425027537379697175891898898898584619028294547488',
    ['ESTONIA  R', 'BCDFGHJKLM', 'PQUVWXYZ./']
  ) == 'string'
);

unstraddle("34045747525284613427502840425027537379697175891898898898584619028294547488",["ESTONIA R", "BCDFGHJKLM", "PQUVWXYZ./"]) should return "ONENIGHTITWASONTHETWENTIETHOFMARCH1888IWASRETURNING.".

assert.equal(
  unstraddle(
    '34045747525284613427502840425027537379697175891898898898584619028294547488',
    ['ESTONIA  R', 'BCDFGHJKLM', 'PQUVWXYZ./']
  ),
  'ONENIGHTITWASONTHETWENTIETHOFMARCH1888IWASRETURNING.'
);

unstraddle("139539363509369743061399059745399365901344308320791798798798367430685972839363935",["HOL MES RT", "ABCDFGIJKN", "PQUVWXYZ./"]) should return "ONENIGHTITWASONTHETWENTIETHOFMARCH1888IWASRETURNING".

assert.equal(
  unstraddle(
    '139539363509369743061399059745399365901344308320791798798798367430685972839363935',
    ['HOL MES RT', 'ABCDFGIJKN', 'PQUVWXYZ./']
  ),
  'ONENIGHTITWASONTHETWENTIETHOFMARCH1888IWASRETURNING'
);

unstraddle("125021250212707204372221327070218600960021823809623283724002424935226226962262521636094232328463769",["ET AON RIS", "BCDFGHJKLM", "PQ/UVWXYZ."]) should return "THECHECKERBOARDCAKERECIPESPECIFIES3LARGEEGGSAND2.25CUPSOFFLOUR.".

assert.equal(
  unstraddle(
    '125021250212707204372221327070218600960021823809623283724002424935226226962262521636094232328463769',
    ['ET AON RIS', 'BCDFGHJKLM', 'PQ/UVWXYZ.']
  ),
  'THECHECKERBOARDCAKERECIPESPECIFIES3LARGEEGGSAND2.25CUPSOFFLOUR.'
);

--seed--

--seed-contents--

function straddle(message, alphabet) {

}

function unstraddle(message, alphabet) {

}

--solutions--

function straddle(message, alphabet) {
  var prefixes = new Array(
    '',
    alphabet[0].indexOf(' '),
    alphabet[0].lastIndexOf(' ')
  );

  var out = '';
  message = message.toUpperCase();
  message = message.replace(/([0-9])/g, '/$1'); // dumb way to escape numbers
  for (var i = 0; i < message.length; i++) {
    var chr = message[i];
    if (chr == ' ') continue;
    for (var j = 0; j < 3; j++) {
      var k = alphabet[j].indexOf(chr);
      if (k < 0) continue;
      out += prefixes[j].toString() + k;
    }
    if (chr == '/') out += message[++i];
  }
  return out;
}
function unstraddle(message, alphabet) {
  var prefixes = new Array(
    '',
    alphabet[0].indexOf(' '),
    alphabet[0].lastIndexOf(' ')
  );
  var out = '';
  var n, o;
  for (var i = 0; i < message.length; i++) {
    n = message[i] * 1;
    switch (n) {
      case prefixes[1]:
        o = alphabet[1][message[++i]];
        break;
      case prefixes[2]:
        o = alphabet[2][message[++i]];
        break;
      default:
        o = alphabet[0][n];
    }
    o == '/' ? (out += message[++i]) : (out += o);
  }
  return out;
}

5.6 KiB Raw Blame History