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* Update Problem001.js * Update Problem001.js * Update Problem001.js * Update Problem001.js * Update Problem001.js
24 lines
956 B
JavaScript
24 lines
956 B
JavaScript
// https://projecteuler.net/problem=1
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/* Multiples of 3 and 5
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If we list all the natural numbers below 10 that are multiples of 3 or 5, we get 3, 5, 6, and 9. The sum of these multiples is 23.
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Find the sum of all the multiples of 3 or 5 below the provided parameter value number.
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*/
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// This method uses the nSum function to add the nSum for 3 and 5. However, it needs to subtract the nSum for 15 once to avoid double counting.
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const multiplesThreeAndFive = (num) => {
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if (num < 1) throw new Error('No natural numbers exist below 1')
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num -= 1
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let sum = 0
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// The nSum function calculates the sum of the first n numbers in the sequence with a common difference of num.
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// Here, n is denoted as frequency.
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const nSum = (num, frequency) => (frequency * (frequency + 1) * num) >> 1
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sum += nSum(3, Math.floor(num / 3))
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sum += nSum(5, Math.floor(num / 5))
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sum -= nSum(15, Math.floor(num / 15))
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return sum
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}
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export { multiplesThreeAndFive }
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