66 lines
2.1 KiB
Markdown
66 lines
2.1 KiB
Markdown
---
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id: 5900f3c61000cf542c50fed9
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title: 'Problem 90: Cube digit pairs'
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challengeType: 5
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forumTopicId: 302207
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dashedName: problem-90-cube-digit-pairs
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---
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# --description--
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Each of the six faces on a cube has a different digit (0 to 9) written on it; the same is done to a second cube. By placing the two cubes side-by-side in different positions we can form a variety of 2-digit numbers.
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For example, the square number 64 could be formed:
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<img class="img-responsive center-block" alt="two cubes, one with the number 6 and the other with number 4" src="https://cdn-media-1.freecodecamp.org/project-euler/cube-digit-pairs.png" style="background-color: white; padding: 10px;" />
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In fact, by carefully choosing the digits on both cubes it is possible to display all of the square numbers below one-hundred: 01, 04, 09, 16, 25, 36, 49, 64, and 81.
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For example, one way this can be achieved is by placing {0, 5, 6, 7, 8, 9} on one cube and {1, 2, 3, 4, 8, 9} on the other cube.
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However, for this problem we shall allow the 6 or 9 to be turned upside-down so that an arrangement like {0, 5, 6, 7, 8, 9} and {1, 2, 3, 4, 6, 7} allows for all nine square numbers to be displayed; otherwise it would be impossible to obtain 09.
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In determining a distinct arrangement we are interested in the digits on each cube, not the order.
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<div style="margin-left: 4em;">
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{1, 2, 3, 4, 5, 6} is equivalent to {3, 6, 4, 1, 2, 5}<br>
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{1, 2, 3, 4, 5, 6} is distinct from {1, 2, 3, 4, 5, 9}
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</div>
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But because we are allowing 6 and 9 to be reversed, the two distinct sets in the last example both represent the extended set {1, 2, 3, 4, 5, 6, 9} for the purpose of forming 2-digit numbers.
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How many distinct arrangements of the two cubes allow for all of the square numbers to be displayed?
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# --hints--
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`cubeDigitPairs()` should return a number.
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```js
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assert(typeof cubeDigitPairs() === 'number');
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```
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`cubeDigitPairs()` should return 1217.
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```js
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assert.strictEqual(cubeDigitPairs(), 1217);
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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 cubeDigitPairs() {
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return true;
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}
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cubeDigitPairs();
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```
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# --solutions--
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```js
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// solution required
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```
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