127 lines
2.5 KiB
Markdown
127 lines
2.5 KiB
Markdown
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---
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id: 5
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localeTitle: 5900f3951000cf542c50fea8
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challengeType: 5
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title: 'Problem 41: Pandigital prime'
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---
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## Description
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<section id='description'>
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Diremos que un número de <i>n</i> dígitos es pandigital si utiliza todos los dígitos 1 a <i>n</i> exactamente una vez. Por ejemplo, 2143 es un pandigital de 4 dígitos y también es primo.
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¿Cuál es el mayor <i>n</i> -Longitud primer Pandigital dígitos que existe?
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</section>
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## Instructions
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<section id='instructions'>
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</section>
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## Tests
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<section id='tests'>
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```yml
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tests:
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- text: <code>pandigitalPrime(4)</code> debe devolver 4231.
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testString: 'assert(pandigitalPrime(4) == 4231, "<code>pandigitalPrime(4)</code> should return 4231.");'
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- text: <code>pandigitalPrime(7)</code> debe devolver 7652413.
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testString: 'assert(pandigitalPrime(7) == 7652413, "<code>pandigitalPrime(7)</code> should return 7652413.");'
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```
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</section>
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## Challenge Seed
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<section id='challengeSeed'>
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<div id='js-seed'>
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```js
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function pandigitalPrime(n) {
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// Good luck!
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return n;
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}
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pandigitalPrime(7);
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```
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</div>
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</section>
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## Solution
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<section id='solution'>
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```js
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function pandigitalPrime(n) {
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function isPrime(num) {
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for (let i = 2, s = Math.sqrt(num); i <= s; i++) {
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if (num % i === 0) {
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return false;
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}
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}
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return num !== 1;
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}
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function getPermutations(n) {
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if (n === 1) {
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permutations.push(digitsArr.join(''));
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} else {
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for (let i = 0; i < n - 1; i++) {
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getPermutations(n - 1);
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// swap(n % 2 === 0 ? i : 0, n - 1);
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if (n % 2 === 0) {
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swap(i, n - 1);
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} else {
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swap(0, n - 1);
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}
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}
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getPermutations(n - 1);
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}
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}
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function swap(x, y) {
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let temp = digitsArr[x];
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digitsArr[x] = digitsArr[y];
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digitsArr[y] = temp;
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}
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let max = 0;
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let permutations = [];
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let digitsArr;
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let pandigitalNum = ";
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for (let max = n; max > 0; max--) {
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pandigitalNum += max;
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}
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for (let i = 0; i < pandigitalNum.length; i++) {
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if (max > 0) {
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break;
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} else {
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permutations = [];
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const currMax = pandigitalNum.slice(i);
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digitsArr = currMax.split('');
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getPermutations(digitsArr.length);
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// sort permutations in descending order
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permutations.sort(function(a, b) {
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return b - a;
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});
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for (let perm of permutations) {
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const thisPerm = parseInt(perm);
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if (isPrime(thisPerm)) {
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max = thisPerm;
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break;
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}
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}
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}
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}
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return max;
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}
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```
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</section>
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