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---
id: a7bf700cd123b9a54eef01d5
title: 請不要重複
challengeType: 5
forumTopicId: 16037
dashedName: no-repeats-please
---
# --description--
返回沒有重複連續字母的提供字符串的總排列數。 假設提供的字符串中的所有字符都是唯一的。
例如,`aab` 應該返回 2因爲它有 6 個排列(`aab``aab``aba``aba``baa``baa`),但其中只有 2 個(`aba``aba`)沒有重複相同字符(即 `a`)。
# --hints--
`permAlone("aab")` 應返回 2。
```js
assert.isNumber(permAlone('aab'));
```
`permAlone("aab")` 應該返回 2。
```js
assert.strictEqual(permAlone('aab'), 2);
```
`permAlone("aaa")` 應該返回 0。
```js
assert.strictEqual(permAlone('aaa'), 0);
```
`permAlone("aabb")`應返回 8。
```js
assert.strictEqual(permAlone('aabb'), 8);
```
`permAlone("abcdefa")`應返回 3600。
```js
assert.strictEqual(permAlone('abcdefa'), 3600);
```
`permAlone("abfdefa")`應該返回 2640。
```js
assert.strictEqual(permAlone('abfdefa'), 2640);
```
`permAlone("zzzzzzzz")` 應返回 0。
```js
assert.strictEqual(permAlone('zzzzzzzz'), 0);
```
`permAlone("a")` 應該返回 1。
```js
assert.strictEqual(permAlone('a'), 1);
```
`permAlone("aaab")` 應該返回 0。
```js
assert.strictEqual(permAlone('aaab'), 0);
```
`permAlone("aaabb")` 應返回 12.
```js
assert.strictEqual(permAlone('aaabb'), 12);
```
# --seed--
## --seed-contents--
```js
function permAlone(str) {
return str;
}
permAlone('aab');
```
# --solutions--
```js
function permAlone(str) {
return permuter(str).filter(function(perm) {
return !perm.match(/(.)\1/g);
}).length;
}
function permuter(str) {
// http://staff.roguecc.edu/JMiller/JavaScript/permute.html
//permArr: Global array which holds the list of permutations
//usedChars: Global utility array which holds a list of "currently-in-use" characters
var permArr = [], usedChars = [];
function permute(input) {
//convert input into a char array (one element for each character)
var i, ch, chars = input.split("");
for (i = 0; i < chars.length; i++) {
//get and remove character at index "i" from char array
ch = chars.splice(i, 1);
//add removed character to the end of used characters
usedChars.push(ch);
//when there are no more characters left in char array to add, add used chars to list of permutations
if (chars.length === 0) permArr[permArr.length] = usedChars.join("");
//send characters (minus the removed one from above) from char array to be permuted
permute(chars.join(""));
//add removed character back into char array in original position
chars.splice(i, 0, ch);
//remove the last character used off the end of used characters array
usedChars.pop();
}
}
permute(str);
return permArr;
}
permAlone('aab');
```