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October 14, 2019 13:39
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Sieve for finding prime numbers
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const arrayOfN = n => Array(n).fill(false).map((n, i) => i + 1); | |
const isNotDivisor = (a, b) => a === b || a % b !== 0; | |
const getPrimeNumbers = maxValue => { | |
const maxIndex = Math.floor(Math.sqrt(maxValue)); | |
let numbersToTest = arrayOfN(maxIndex); | |
let range = arrayOfN(maxValue); | |
numbersToTest.splice(0, 1); | |
numbersToTest.forEach(outerNtt => { | |
numbersToTest = numbersToTest.filter(innerNtt => isNotDivisor(innerNtt, outerNtt)); | |
}); | |
numbersToTest.forEach(ntt => { | |
range = range.filter(n => isNotDivisor(n, ntt)); | |
}); | |
return range; | |
} | |
const getPrimeNumbersUnoptimized = maxValue => { | |
const maxIndex = Math.floor(Math.sqrt(maxValue)); | |
let range = arrayOfN(maxValue); | |
let index = 2; | |
while (index <= maxIndex) { | |
range = range.filter(n => isNotDivisor(n, index)) | |
index ++; | |
} | |
return range; | |
} | |
console.time('Normal'); | |
getPrimeNumbersUnoptimized(10000); | |
console.timeEnd('Normal'); | |
console.time('Optimized'); | |
getPrimeNumbers(10000); | |
console.timeEnd('Optimized'); |
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