38 lines
1.2 KiB
Markdown
38 lines
1.2 KiB
Markdown
---
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title: String permutations
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type: snippet
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tags: [string,recursion]
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cover: mac-and-coffee
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dateModified: 2020-11-15T17:13:42+02:00
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---
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Generates all permutations of a string (contains duplicates).
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- Use recursion.
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- For each letter in the given string, create all the partial permutations for the rest of its letters.
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- Use `Array.prototype.map()` to combine the letter with each partial permutation.
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- Use `Array.prototype.reduce()` to combine all permutations in one array.
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- Base cases are for `String.prototype.length` equal to `2` or `1`.
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- ⚠️ **WARNING**: The execution time increases exponentially with each character. Anything more than 8 to 10 characters will cause your environment to hang as it tries to solve all the different combinations.
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```js
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const stringPermutations = str => {
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if (str.length <= 2) return str.length === 2 ? [str, str[1] + str[0]] : [str];
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return str
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.split('')
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.reduce(
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(acc, letter, i) =>
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acc.concat(
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stringPermutations(str.slice(0, i) + str.slice(i + 1)).map(
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val => letter + val
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)
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),
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[]
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);
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};
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```
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```js
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stringPermutations('abc'); // ['abc', 'acb', 'bac', 'bca', 'cab', 'cba']
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```
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