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id	title	challengeType	forumTopicId	dashedName
5a23c84252665b21eecc8046	Symmetric difference	5	16086	symmetric-difference

--description--

Given two sets A and B, compute (A \\setminus B) \\cup (B \\setminus A). That is, enumerate the items that are in A or B but not both. This set is called the [symmetric difference](https://en.wikipedia.org/wiki/Symmetric difference) of A and B. In other words: (A \\cup B) \\setminus (A \\cap B) (the set of items that are in at least one of A or B minus the set of items that are in both A and B).

--instructions--

Write a function that takes two arrays as parameters and returns the symmetric difference. Sort the resultant array before returning it.

--hints--

symmetricDifference should be a function.

assert(typeof symmetricDifference == 'function');

symmetricDifference(["John", "Bob", "Mary", "Serena"], ["Jim", "Mary", "John", "Bob"]) should return an array.

assert(
  Array.isArray(
    symmetricDifference(
      ['John', 'Bob', 'Mary', 'Serena'],
      ['Jim', 'Mary', 'John', 'Bob']
    )
  )
);

symmetricDifference(["John", "Bob", "Mary", "Serena"], ["Jim", "Mary", "John", "Bob"]) should return ["Jim", "Serena"].

assert.deepEqual(
  symmetricDifference(
    ['John', 'Bob', 'Mary', 'Serena'],
    ['Jim', 'Mary', 'John', 'Bob']
  ),
  ['Jim', 'Serena']
);

symmetricDifference([1, 2, 3], [3, 4]) should return [1, 2, 4].

assert.deepEqual(symmetricDifference([1, 2, 3], [3, 4]), [1, 2, 4]);

symmetricDifference([1, 2, 3, 4, 5], [3, 4, 8, 7]) should return [1, 2, 5, 7, 8].

assert.deepEqual(symmetricDifference([1, 2, 3, 4, 5], [3, 4, 8, 7]), [
  1,
  2,
  5,
  7,
  8
]);

symmetricDifference([1, 2, 3, 4, 5, 6, 7, 8], [1, 3, 5, 6, 7, 8, 9]) should return [2, 4, 9].

assert.deepEqual(
  symmetricDifference([1, 2, 3, 4, 5, 6, 7, 8], [1, 3, 5, 6, 7, 8, 9]),
  [2, 4, 9]
);

symmetricDifference([1, 2, 4, 7, 9], [2, 3, 7, 8, 9]) should return [1, 3, 4, 8].

assert.deepEqual(symmetricDifference([1, 2, 4, 7, 9], [2, 3, 7, 8, 9]), [
  1,
  3,
  4,
  8
]);

--seed--

--seed-contents--

function symmetricDifference(A, B) {

}

--solutions--

function symmetricDifference(A, B) {
  function relative_complement(A, B) {
    return A.filter(function(elem) {
      return B.indexOf(elem) == -1;
    });
  }

  function unique(ary) {
    var u = ary.concat().sort();
    for (var i = 1; i < u.length; ) {
      if (u[i - 1] === u[i]) u.splice(i, 1);
      else i++;
    }
    return u;
  }

  return unique(
    relative_complement(A, B).concat(relative_complement(B, A))
  ).sort();
}

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