【2018/07/29 TokyuRuby会議12】Project Eulerから生まれたワンライナーたち

by Shu OGAWARA

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Project Euler͔Βੜ·Εͨ ϫϯϥΠφʔͨͪ Shu OGAWARA (@expajp) TokyuRubyձٞ12 2018/07/29 Sun.

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ࣗݾ঺հ • Shu OGAWARA (@expajp) – Ruby/Railsྺ 1೥΄Ͳ – ग़਎ɿௗऔɺֶੜ࣌୅ɿਆށ – ϦϯΧʔζ – झຯͰ߹এஂʹॴଐ 1

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Project Eulerͬͯ஌ͬͯ·͔͢ʁ 2

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ϨΦϯϋϧτɾΦΠϥʔ (1707-1783) • εΠεͷ਺ֶऀ • ࿦จࣥච଎౓͸800ϖʔδ/೥ • ۀ੷͕๲େ͗ͯ͢ 100೥ܦͬͯ΋શू͕ະ׬ 3

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Project Euler • ίϯϐϡʔλͰղ͘਺ֶͷ໰୊ू – ϓϩίϯతͳ໰୊ – ͚ͩͲͬ͘͡Γղ͚Δ 5

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Project Euler • RubyͰͷ௅ઓऀ͸൪໨ʹଟ͍ – Python, C/C++, Java, C#, Haskellʹଓ͍ͯRuby – ϓϩϑΟʔϧʹݴޠΛॻ͍͍ͯΔਓͷ౷ܭ 6

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7 ൃදऀ͸234Ґʢ95໰ղ౴ʣ

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8 ൃදऀ͸234Ґʢ95໰ղ౴ʣ

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ϫϯϥΠφʔ • 1ߦͰॻ͘ϓϩάϥϜͷ͜ͱ – ʢࣗ෼ͷதͰ͸ʣϥΠϒϥϦಡࠐ͸ؚ·ͳ͍ • Rubyͷ୉ޣຯ • ͨͱ͑͹FizzBuzz 9

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͜ͷൃදͷझࢫ • Project EulerΛ100໰ۙ͘·Ͱղ͍͖ͯͨͷ ͰɺϫϯϥΠφʔͰղ͚Δ໰୊ΛνϣΠε ΈΜͳʹղ͍ͯ΋Β͏ – ղ౴ྫΛ঺հ 10

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͜ͷൃදͷझࢫ • Project EulerΛ100໰ۙ͘·Ͱղ͍͖ͯͨͷ ͰɺϫϯϥΠφʔͰղ͚Δ໰୊ΛνϣΠε ΈΜͳʹղ͍ͯ΋Β͏ – ղ౴ྫΛ঺հ 11 – ΈΜͳʹղ͍ͯ΋Β͏

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ਲͬ෷͏! લʹΞλϚ࢖͍·͠ΐ͏ʂ 12

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Please Get Ready 13 $ irb OR $ pry $ rib OR

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Are You Ready ? 14

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ୈ̍໰ (30sec. Hint: 15sec.) 1, 2, …, 10 ʹ͍ͭͯ, ೋ৐ͷ࿨͸, 12 + 22 + ... + 102 = 385 ࿨ͷೋ৐͸, (1 + 2 + ... + 10)2 = 3025 ࠩ͸ 3025 - 385 = 2640 ͱͳΔ. ಉ༷ʹͯ͠, 1, 2, …, 100ʹ͍ͭͯʮೋ৐ͷ࿨ʯͱʮ࿨ͷೋ৐ʯ ͷࠩΛٻΊΑ. ग़యɿProject Euler – Problem 6 15

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ղ౴ྫ 17

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ୈ̎໰ (1min. Hint: 30sec.) 20ੈلʢ1901೥1݄1೔͔Β2000೥12݄31೔ʣதʹ ݄ͷॳΊ͕೔༵೔ʹͳΔͷ͸Կճ͋Δ͔ ͳ͓, ೥1݄1೔͸݄༵೔Ͱ͋Γ, 20ੈلʹ͓͍ͯ4ͷഒ਺ͷ೥͸ඞͣ͏Δ͏೥Ͱ͋Δ. ग़య: Project Euler - Problem 19 18

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ୈ̎໰ (1min. Hint: 30sec.) 20ੈلʢ1901೥1݄1೔͔Β2000೥12݄31೔ʣதʹ ݄ͷॳΊ͕೔༵೔ʹͳΔͷ͸Կճ͋Δ͔ ͳ͓, ೥1݄1೔͸݄༵೔Ͱ͋Γ, 20ੈلʹ͓͍ͯ4ͷഒ਺ͷ೥͸ඞͣ͏Δ͏೥Ͱ͋Δ. ग़య: Project Euler - Problem 19 19 ώϯτɿϥΠϒϥϦಡࠐ͸ϫϯϥΠφʔʹؚΈ·ͤΜ

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ղ౴ྫ 20 DateϥΠϒϥϦͷಡࠐ͕ඞཁ

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࣮͸ɺϥΠϒϥϦͳ͠Ͱ΍Δํ๏΋͋Δ 21

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ղ౴ྫ2 22

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ղઆ͸ͦͷ͏ͪϒϩάʹͰ΋ॻ͖·͢! 23

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·ͱΊ • 1SPKFDU &VMFS͸ͨͷ͍͠ • ϫϯϥΠφʔͰղ͘ͱ΋ͬͱͨͷ͍͠ • ࢓ࣄͷ߹ؒʹΞλϚͷମૢ͸͍͔͕Ͱ͔͢ 24

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Thank you for Listening!! 25 Ruby Logo(https://www.ruby-lang.org/ja/ ) CC BY-NC-SA 2.5