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86d333ee94
* chore: Switch to Node 20 + Vitest * chore: migrate to vitest mock functions * chore: code style (switch to prettier) * test: re-enable long-running test Seems the switch to Node 20 and Vitest has vastly improved the code's and / or the test's runtime! see #1193 * chore: code style * chore: fix failing tests * Updated Documentation in README.md * Update contribution guidelines to state usage of Prettier * fix: set prettier printWidth back to 80 * chore: apply updated code style automatically * fix: set prettier line endings to lf again * chore: apply updated code style automatically --------- Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com> Co-authored-by: Lars Müller <34514239+appgurueu@users.noreply.github.com>
19 lines
663 B
JavaScript
19 lines
663 B
JavaScript
// https://projecteuler.net/problem=2
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const SQ5 = 5 ** 0.5 // Square root of 5
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const PHI = (1 + SQ5) / 2 // definition of PHI
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// theoretically it should take O(1) constant amount of time as long
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// arithmetic calculations are considered to be in constant amount of time
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export const EvenFibonacci = (limit) => {
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if (limit < 1)
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throw new Error("Fibonacci sequence limit can't be less than 1")
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const highestIndex = Math.floor(Math.log(limit * SQ5) / Math.log(PHI))
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const n = Math.floor(highestIndex / 3)
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return Math.floor(
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((PHI ** (3 * n + 3) - 1) / (PHI ** 3 - 1) -
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((1 - PHI) ** (3 * n + 3) - 1) / ((1 - PHI) ** 3 - 1)) /
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SQ5
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)
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}
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