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Problem Explanation:

Symmetric Difference is the difference between two sets.

So in the Symmetric Difference Bonfire you would work through the arrays of numbers something like this -

sym(A, B, C) Translates to sym(sym(A,B),C)

Or in plain English - First find the Symmetric Difference of Set A and Set B. Then find the Symmetric Difference of this new set and Set C.

So -

sym([1, 2, 5], [2, 3, 5], [3, 4, 5])

would equal

[1,4,5]

Here's a nice video tutorial (with an awful fake British accent!) -

YouTube - Symmetric Difference

Hint: 1

The arguments object is not an Array. It is similar to an Array, but does not have any Array properties except length. For example, it does not have the pop method. However it can be converted to a real Array:

var args = Array.prototype.slice.call(arguments);

Hint: 2

Write a function that returns the symmetric difference of array1 and array2.

yourFunction([1, 2, 3], [2, 4, 6]) must return [1, 3, 4, 6]

Hint: 3

Use Array.prototype.reduce along with yourFunction to repeat the process on multiple arguments

Something a bit strange about the definition of symmetric difference is that if one identical item occurs in three different sets, it is a member of the symmetric difference. An example is easier to explain:

a = [1, 2, 5]
b = [2, 3, 5]
c = [3, 4, 5]

sym(a, b) = [1, 3]
sym([1, 3], c) = [1, 4, 5]

Spoiler Alert!

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Solution ahead!

Code Solution:

function sym() {

  // Convert the argument object into a proper array
  var args = Array.prototype.slice.call(arguments);

  // Return the symmetric difference of 2 arrays
  var getDiff = function(arr1, arr2) {

    // Returns items in arr1 that don't exist in arr2
    function filterFunction(arr1, arr2) {
      return arr1.filter(function(item) {
        return arr2.indexOf(item) === -1;
      });
    }

    // Run filter function on each array against the other
    return filterFunction(arr1, arr2)
      .concat(filterFunction(arr2, arr1));
  };

  // Reduce all arguments getting the difference of them
  return args.reduce(getDiff, []);
}

Code Explanation:

  • Read comments in code.

Related Links

Credits:

If you found this page useful, you can give thanks by copying and pasting this on the main chat: thanks @Rafase282 @guyjoseph @jjmax75 for your help with Bonfire: Symmetric Difference

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