127 lines
2.9 KiB
Markdown
127 lines
2.9 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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forumTopicId: 16037
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dashedName: no-repeats-please
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---
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# --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, `aab` should return 2 because it has 6 total permutations (`aab`, `aab`, `aba`, `aba`, `baa`, `baa`), but only 2 of them (`aba` and `aba`) don't have the same letter (in this case `a`) repeating.
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# --hints--
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`permAlone("aab")` should return a number.
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```js
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assert.isNumber(permAlone('aab'));
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```
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`permAlone("aab")` should return 2.
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```js
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assert.strictEqual(permAlone('aab'), 2);
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```
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`permAlone("aaa")` should return 0.
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```js
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assert.strictEqual(permAlone('aaa'), 0);
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```
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`permAlone("aabb")` should return 8.
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```js
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assert.strictEqual(permAlone('aabb'), 8);
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```
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`permAlone("abcdefa")` should return 3600.
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```js
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assert.strictEqual(permAlone('abcdefa'), 3600);
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```
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`permAlone("abfdefa")` should return 2640.
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```js
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assert.strictEqual(permAlone('abfdefa'), 2640);
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```
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`permAlone("zzzzzzzz")` should return 0.
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```js
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assert.strictEqual(permAlone('zzzzzzzz'), 0);
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```
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`permAlone("a")` should return 1.
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```js
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assert.strictEqual(permAlone('a'), 1);
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```
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`permAlone("aaab")` should return 0.
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```js
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assert.strictEqual(permAlone('aaab'), 0);
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```
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`permAlone("aaabb")` should return 12.
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```js
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assert.strictEqual(permAlone('aaabb'), 12);
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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 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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# --solutions--
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```js
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function permAlone(str) {
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return permuter(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 permuter(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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