111 lines
4.1 KiB
Markdown
111 lines
4.1 KiB
Markdown
---
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id: a7bf700cd123b9a54eef01d5
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title: No Repeats Please
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challengeType: 5
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---
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## Description
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<section id='description'>
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Return the number of total permutations of the provided string that don't have repeated consecutive letters. Assume that all characters in the provided string are each unique.
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For example, <code>aab</code> should return 2 because it has 6 total permutations (<code>aab</code>, <code>aab</code>, <code>aba</code>, <code>aba</code>, <code>baa</code>, <code>baa</code>), but only 2 of them (<code>aba</code> and <code>aba</code>) don't have the same letter (in this case <code>a</code>) repeating.
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Remember to use <a href='http://forum.freecodecamp.org/t/how-to-get-help-when-you-are-stuck/19514' target='_blank'>Read-Search-Ask</a> if you get stuck. Try to pair program. Write your own code.
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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>permAlone("aab")</code> should return a number.
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testString: assert.isNumber(permAlone('aab'), '<code>permAlone("aab")</code> should return a number.');
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- text: <code>permAlone("aab")</code> should return 2.
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testString: assert.strictEqual(permAlone('aab'), 2, '<code>permAlone("aab")</code> should return 2.');
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- text: <code>permAlone("aaa")</code> should return 0.
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testString: assert.strictEqual(permAlone('aaa'), 0, '<code>permAlone("aaa")</code> should return 0.');
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- text: <code>permAlone("aabb")</code> should return 8.
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testString: assert.strictEqual(permAlone('aabb'), 8, '<code>permAlone("aabb")</code> should return 8.');
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- text: <code>permAlone("abcdefa")</code> should return 3600.
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testString: assert.strictEqual(permAlone('abcdefa'), 3600, '<code>permAlone("abcdefa")</code> should return 3600.');
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- text: <code>permAlone("abfdefa")</code> should return 2640.
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testString: assert.strictEqual(permAlone('abfdefa'), 2640, '<code>permAlone("abfdefa")</code> should return 2640.');
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- text: <code>permAlone("zzzzzzzz")</code> should return 0.
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testString: assert.strictEqual(permAlone('zzzzzzzz'), 0, '<code>permAlone("zzzzzzzz")</code> should return 0.');
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- text: <code>permAlone("a")</code> should return 1.
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testString: assert.strictEqual(permAlone('a'), 1, '<code>permAlone("a")</code> should return 1.');
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- text: <code>permAlone("aaab")</code> should return 0.
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testString: assert.strictEqual(permAlone('aaab'), 0, '<code>permAlone("aaab")</code> should return 0.');
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- text: <code>permAlone("aaabb")</code> should return 12.
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testString: assert.strictEqual(permAlone('aaabb'), 12, '<code>permAlone("aaabb")</code> should return 12.');
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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 permAlone(str) {
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return str;
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}
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permAlone('aab');
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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 permAlone(str) {
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return permutor(str).filter(function(perm) {
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return !perm.match(/(.)\1/g);
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}).length;
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}
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function permutor(str) {
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// http://staff.roguecc.edu/JMiller/JavaScript/permute.html
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//permArr: Global array which holds the list of permutations
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//usedChars: Global utility array which holds a list of "currently-in-use" characters
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var permArr = [], usedChars = [];
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function permute(input) {
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//convert input into a char array (one element for each character)
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var i, ch, chars = input.split("");
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for (i = 0; i < chars.length; i++) {
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//get and remove character at index "i" from char array
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ch = chars.splice(i, 1);
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//add removed character to the end of used characters
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usedChars.push(ch);
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//when there are no more characters left in char array to add, add used chars to list of permutations
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if (chars.length === 0) permArr[permArr.length] = usedChars.join("");
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//send characters (minus the removed one from above) from char array to be permuted
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permute(chars.join(""));
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//add removed character back into char array in original position
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chars.splice(i, 0, ch);
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//remove the last character used off the end of used characters array
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usedChars.pop();
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}
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}
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permute(str);
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return permArr;
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}
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permAlone('aab');
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```
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</section>
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