diff --git a/snippets/factors.md b/snippets/factors.md index 0a8d32d24..dbe56a1b8 100644 --- a/snippets/factors.md +++ b/snippets/factors.md @@ -1,42 +1,35 @@ ### factors -Returns the array of factors of the given `int`. If the second argument is set to `true` returns only the prime factors of `int`.If the third argument is set to `true` will return an array of arrays each containing two elements, the `factor` and the number of times the `factor` divides `int`. -If `int` is `1` or `0` returns an empty array. -If `int` is less than `0` returns all the factors of `-int` together with their `additive inverses`. +Returns the array of factors of the given `num`. +If the second argument is set to `true` returns only the prime factors of `num`. +If `num` is `1` or `0` returns an empty array. +If `num` is less than `0` returns all the factors of `-int` together with their additive inverses. + +Use `Array.from()`, `Array.map()` and `Array.filter()` to find all the factors of `num`. +If given `num` is negative, use `Array.reduce()` to add the additive inverses to the array. +Return all results if `primes` is `false`, else determine and return only the prime factors using `isPrime` and `Array.filter()`. +Omit the second argument, `primes`, to return prime and non-prime factors by default. **Note**:- _Negative numbers are not considered prime._ + ``` js -const factors = (int,prime = false,powers = false) => { - const howManyTimes = (num,divisor) => { - if([1,0].includes(divisor)) return Infinity - let i = 0 - while(Number.isInteger(num/divisor)){ - i++ - num = num / divisor - } - return i - } +const factors = (num, primes = false) => { const isPrime = num => { - const boundary = Math.floor(Math.sqrt(num)); - for (var i = 2; i <= boundary; i++) if (num % i === 0) return false; - return num >= 2 + const boundary = Math.floor(Math.sqrt(num)); + for (var i = 2; i <= boundary; i++) if (num % i === 0) return false; + return num >= 2; } - let isNeg = int < 0; - int = isNeg ? -int : int; - let array = Array.from({length: int - 1}).map((val,i) => int % (i+2) === 0 ? (i+2) : false).filter(val => val); + const isNeg = num < 0; + num = isNeg ? -num : num; + let array = Array.from({length: num - 1}).map((val,i) => num % (i+2) === 0 ? (i+2) : false).filter(val => val); if(isNeg) array = array.reduce((acc,val) => {acc.push(val); acc.push(-val); return acc}, []); - array = prime ? array.filter(el => isPrime(el)) : array; - return powers ? array.map(x => [x,howManyTimes(int,x)]) : array + return primes ? array.filter(isPrime) : array; } ``` ```js -factors(12); //[2,3,4,6,12] -factors(12,true); //[2,3] -factors(12,true,true); //[[2,2], [3,1]] -factors(12,false,true); //[[2,2], [3,1], [4,1], [6,1], [12,1]] -factors(-12); //[2, -2, 3, -3, 4, -4, 6, -6, 12, -12] -factors(12,true); //[2,3] -factors(12,true,true); //[[2,2], [3,1]] -factors(12,false,true); //[[2,2], [-2,2], [3,1], [-3,1], [4,1], [-4,1], [6,1], [-6,1], [12,1], [-12,1]] +factors(12); // [2,3,4,6,12] +factors(12,true); // [2,3] +factors(-12); // [2, -2, 3, -3, 4, -4, 6, -6, 12, -12] +factors(-12, true); // [2,3] ```