2018-09-30 22:01:58 +00:00
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---
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id: 5900f3701000cf542c50fe83
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challengeType: 5
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title: 'Problem 4: Largest palindrome product'
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2019-08-05 16:17:33 +00:00
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forumTopicId: 302065
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2018-09-30 22:01:58 +00:00
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---
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## Description
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<section id='description'>
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A palindromic number reads the same both ways. The largest palindrome made from the product of two 2-digit numbers is 9009 = 91 × 99.
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Find the largest palindrome made from the product of two <code>n</code>-digit numbers.
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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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2018-10-04 13:37:37 +00:00
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tests:
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- text: <code>largestPalindromeProduct(2)</code> should return 9009.
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2019-07-27 02:41:55 +00:00
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testString: assert.strictEqual(largestPalindromeProduct(2), 9009);
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2018-10-04 13:37:37 +00:00
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- text: <code>largestPalindromeProduct(3)</code> should return 906609.
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2019-07-27 02:41:55 +00:00
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testString: assert.strictEqual(largestPalindromeProduct(3), 906609);
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2018-09-30 22:01:58 +00:00
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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 largestPalindromeProduct(n) {
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// Good luck!
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return true;
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}
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largestPalindromeProduct(3);
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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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const largestPalindromeProduct = (digit)=>{
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let start = 1;
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let end = Number(`1e${digit}`) - 1;
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let palindrome = [];
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for(let i=start;i<=end;i++){
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for(let j=start;j<=end;j++){
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let product = i*j;
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let palindromeRegex = /\b(\d)(\d?)(\d?).?\3\2\1\b/gi;
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palindromeRegex.test(product) && palindrome.push(product);
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}
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}
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return Math.max(...palindrome);
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}
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```
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</section>
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