0425ebefe7
Cleaned up the current snippets for consistency and minor problems, added multiple tags to most of them, archived a few.
43 lines
1.5 KiB
Markdown
43 lines
1.5 KiB
Markdown
### factors
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Returns the array of factors of the given `num`.
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If the second argument is set to `true` returns only the prime factors of `num`.
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If `num` is `1` or `0` returns an empty array.
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If `num` is less than `0` returns all the factors of `-int` together with their additive inverses.
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Use `Array.from()`, `Array.map()` and `Array.filter()` to find all the factors of `num`.
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If given `num` is negative, use `Array.reduce()` to add the additive inverses to the array.
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Return all results if `primes` is `false`, else determine and return only the prime factors using `isPrime` and `Array.filter()`.
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Omit the second argument, `primes`, to return prime and non-prime factors by default.
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**Note**:- _Negative numbers are not considered prime._
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```js
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const factors = (num, primes = false) => {
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const isPrime = num => {
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const boundary = Math.floor(Math.sqrt(num));
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for (var i = 2; i <= boundary; i++) if (num % i === 0) return false;
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return num >= 2;
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};
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const isNeg = num < 0;
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num = isNeg ? -num : num;
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let array = Array.from({ length: num - 1 })
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.map((val, i) => (num % (i + 2) === 0 ? i + 2 : false))
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.filter(val => val);
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if (isNeg)
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array = array.reduce((acc, val) => {
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acc.push(val);
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acc.push(-val);
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return acc;
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}, []);
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return primes ? array.filter(isPrime) : array;
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};
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```
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```js
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factors(12); // [2,3,4,6,12]
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factors(12, true); // [2,3]
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factors(-12); // [2, -2, 3, -3, 4, -4, 6, -6, 12, -12]
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factors(-12, true); // [2,3]
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```
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