ee1e8abd87
* feat(tools): add seed/solution restore script * chore(curriculum): remove empty sections' markers * chore(curriculum): add seed + solution to Chinese * chore: remove old formatter * fix: update getChallenges parse translated challenges separately, without reference to the source * chore(curriculum): add dashedName to English * chore(curriculum): add dashedName to Chinese * refactor: remove unused challenge property 'name' * fix: relax dashedName requirement * fix: stray tag Remove stray `pre` tag from challenge file. Signed-off-by: nhcarrigan <nhcarrigan@gmail.com> Co-authored-by: nhcarrigan <nhcarrigan@gmail.com>
151 lines
3.8 KiB
Markdown
151 lines
3.8 KiB
Markdown
---
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id: a3f503de51cf954ede28891d
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title: Find the Symmetric Difference
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challengeType: 5
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forumTopicId: 301611
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dashedName: find-the-symmetric-difference
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---
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# --description--
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The mathematical term <dfn>symmetric difference</dfn> (`△` or `⊕`) of two sets is the set of elements which are in either of the two sets but not in both. For example, for sets `A = {1, 2, 3}` and `B = {2, 3, 4}`, `A △ B = {1, 4}`.
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Symmetric difference is a binary operation, which means it operates on only two elements. So to evaluate an expression involving symmetric differences among *three* elements (`A △ B △ C`), you must complete one operation at a time. Thus, for sets `A` and `B` above, and `C = {2, 3}`, `A △ B △ C = (A △ B) △ C = {1, 4} △ {2, 3} = {1, 2, 3, 4}`.
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# --instructions--
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Create a function that takes two or more arrays and returns an array of their symmetric difference. The returned array must contain only unique values (*no duplicates*).
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# --hints--
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`sym([1, 2, 3], [5, 2, 1, 4])` should return `[3, 4, 5]`.
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```js
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assert.sameMembers(sym([1, 2, 3], [5, 2, 1, 4]), [3, 4, 5]);
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```
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`sym([1, 2, 3], [5, 2, 1, 4])` should contain only three elements.
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```js
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assert.equal(sym([1, 2, 3], [5, 2, 1, 4]).length, 3);
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```
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`sym([1, 2, 3, 3], [5, 2, 1, 4])` should return `[3, 4, 5]`.
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```js
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assert.sameMembers(sym([1, 2, 3, 3], [5, 2, 1, 4]), [3, 4, 5]);
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```
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`sym([1, 2, 3, 3], [5, 2, 1, 4])` should contain only three elements.
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```js
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assert.equal(sym([1, 2, 3, 3], [5, 2, 1, 4]).length, 3);
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```
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`sym([1, 2, 3], [5, 2, 1, 4, 5])` should return `[3, 4, 5]`.
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```js
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assert.sameMembers(sym([1, 2, 3], [5, 2, 1, 4, 5]), [3, 4, 5]);
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```
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`sym([1, 2, 3], [5, 2, 1, 4, 5])` should contain only three elements.
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```js
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assert.equal(sym([1, 2, 3], [5, 2, 1, 4, 5]).length, 3);
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```
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`sym([1, 2, 5], [2, 3, 5], [3, 4, 5])` should return `[1, 4, 5]`
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```js
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assert.sameMembers(sym([1, 2, 5], [2, 3, 5], [3, 4, 5]), [1, 4, 5]);
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```
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`sym([1, 2, 5], [2, 3, 5], [3, 4, 5])` should contain only three elements.
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```js
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assert.equal(sym([1, 2, 5], [2, 3, 5], [3, 4, 5]).length, 3);
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```
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`sym([1, 1, 2, 5], [2, 2, 3, 5], [3, 4, 5, 5])` should return `[1, 4, 5]`.
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```js
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assert.sameMembers(sym([1, 1, 2, 5], [2, 2, 3, 5], [3, 4, 5, 5]), [1, 4, 5]);
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```
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`sym([1, 1, 2, 5], [2, 2, 3, 5], [3, 4, 5, 5])` should contain only three elements.
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```js
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assert.equal(sym([1, 1, 2, 5], [2, 2, 3, 5], [3, 4, 5, 5]).length, 3);
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```
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`sym([3, 3, 3, 2, 5], [2, 1, 5, 7], [3, 4, 6, 6], [1, 2, 3])` should return `[2, 3, 4, 6, 7]`.
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```js
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assert.sameMembers(
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sym([3, 3, 3, 2, 5], [2, 1, 5, 7], [3, 4, 6, 6], [1, 2, 3]),
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[2, 3, 4, 6, 7]
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);
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```
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`sym([3, 3, 3, 2, 5], [2, 1, 5, 7], [3, 4, 6, 6], [1, 2, 3])` should contain only five elements.
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```js
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assert.equal(
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sym([3, 3, 3, 2, 5], [2, 1, 5, 7], [3, 4, 6, 6], [1, 2, 3]).length,
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5
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);
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```
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`sym([3, 3, 3, 2, 5], [2, 1, 5, 7], [3, 4, 6, 6], [1, 2, 3], [5, 3, 9, 8], [1])` should return `[1, 2, 4, 5, 6, 7, 8, 9]`.
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```js
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assert.sameMembers(
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sym(
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[3, 3, 3, 2, 5],
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[2, 1, 5, 7],
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[3, 4, 6, 6],
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[1, 2, 3],
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[5, 3, 9, 8],
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[1]
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),
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[1, 2, 4, 5, 6, 7, 8, 9]
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);
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```
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`sym([3, 3, 3, 2, 5], [2, 1, 5, 7], [3, 4, 6, 6], [1, 2, 3], [5, 3, 9, 8], [1])` should contain only eight elements.
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```js
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assert.equal(
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sym([3, 3, 3, 2, 5], [2, 1, 5, 7], [3, 4, 6, 6], [1, 2, 3], [5, 3, 9, 8], [1])
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.length,
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8
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);
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```
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# --seed--
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## --seed-contents--
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```js
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function sym(args) {
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return args;
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}
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sym([1, 2, 3], [5, 2, 1, 4]);
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```
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# --solutions--
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```js
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function sym() {
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var arrays = [].slice.call(arguments);
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return arrays.reduce(function (symDiff, arr) {
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return symDiff.concat(arr).filter(function (val, idx, theArr) {
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return theArr.indexOf(val) === idx
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&& (symDiff.indexOf(val) === -1 || arr.indexOf(val) === -1);
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});
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});
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}
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sym([1, 2, 3], [5, 2, 1, 4]);
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```
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