Laravel Collectionの計算量を調べてみた

by Ryo Tomidokoro

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Laravel CollectionͷܭࢉྔΛௐ΂ͯΈͨ 1)1ษڧձ *OOPWBUPS+BQBO*OD ෋ॴ྄ &OHJOFFS

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ܭࢉྔʹ͍͓ͭͯ͞Β͍ ຊ೔͸࣌ؒతܭࢉྔΛѻ͍·͢

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ྫ͑͹ϨϏϡʔ͍ͯ͠Δ࣌

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ʮ͜ͷॲཧ஗ͦ͏ʯ ͜Εͩͱ෼͔Γʹ͍͘ɻ ॲཧͷ࣌ؒత଎౓Λڞ௨஌ࣝͰ఻͍͑ͨ

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ӳޠͩͱ Time Complexity ࣌ؒෳࡶੑ ϓϩάϥϜͷॲཧʹ ͲΕ͘Β͍͕͔͔࣌ؒΔ͔Λ ਺ֶతʹѻ͏

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Oه๏ O(1) O(log n) O(n) O(n * log n) O(n^2) ϓϩάϥϜͷ࣌ؒతܭࢉྔΛද͢

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Oه๏ σʔλྔ͕૿Ճͨ͠৔߹ͷ ॲཧ࣌ؒͷ૿Ճ܏޲͕෼͔Δ

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[άϥϑҾ༻] ։ൃ৽ଔʹ๋͙ɺجຊͷΞϧΰϦζϜͱܭࢉྔ http://www.techscore.com/blog/2016/08/08/։ൃ৽ଔʹ๋͙ɺجຊͷΞϧΰϦζϜͱܭࢉྔ/ σʔλྔͱܭࢉྔ

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ܭࢉྔͱΞϧΰϦζϜ ΞϧΰϦζϜ ܭࢉྔ όϒϧιʔτ 0 O? Ϛʔδιʔτ 0 OMPHO όΠφϦαʔν 0 MPHO ΞϧΰϦζϜʹΑͬͯܭࢉྔ͕ҟͳΔ

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͞Βʹৄ͘͠஌Γ͍ͨਓ ਺ֶΨʔϧ4 ཚ୒ΞϧΰϦζϜ 2ষͱ6ষΛಡΉ΂͠

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ຊ୊ʹ໭Δ

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Laravel Collection֤ϝιουͷܭࢉྔ ΋͏ͪΐͬͱ͖Ε͍ʹ͠·͢…

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ࡶʹ·ͱΊΔͱ • ΄ͱΜͲ O(n) • O(1) ͕9ݸ • O(n^2) Ҏ্͕8ݸ

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ཁ஫ҙϝιου • collapse O(n^2) • crossJoin O(n^3) • diff O(n^t) • diffAssoc O(n^t) • ﬂatMap O(n^2) • ﬂatten O(n^2) • groupBy O(n^2) • intersect O(n^2)

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࣮ଌͯ͠Έͨ

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where - O(n) ॲཧ࣌ؒ(ඵ) σʔλ݅਺

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count - O(1) ॲཧ࣌ؒ(ඵ) σʔλ݅਺

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collapse - O(n^2) ॲཧ࣌ؒ(ඵ) σʔλ݅਺

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crossJoin - O(n^3) ॲཧ࣌ؒ(ඵ) σʔλ݅਺

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diff - O(n^t) ॲཧ࣌ؒ(ඵ) σʔλ݅਺ t͸ﬁeld਺ʹґଘ͢Δ

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ܭࢉྔ͕෼͔ͬͨͱͯ͠ Կ͔ྑ͍͜ͱ͋Δͷ͔ʁ

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஌Βͳ͍ͱѱ͍͜ͱ͕ى͖Δ

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࣮ࡍʹ͔͋ͬͨ΋͠Εͳ͍ ܭࢉྔ͕໰୊ʹͳͬͨίʔυྫ ※࣮࿩Λݩʹͨ͠ϑΟΫγϣϯͰ͢

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શ݅औಘ ϖʔδϯάͷͨΊʹ શ݅ϧʔϓͰճ͢ ྫ1

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શ݅औಘ ϖʔδϯάͷͨΊʹ શ݅ϧʔϓͰճ͢ ϖʔδͷޙ൒ʹߦ͚͹ߦ͘΄Ͳ ϧʔϓ͕ճͬͯ஗͘ͳΔ O(n) ྫ1

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߹Θٕͤ O(n^2) O(n)ΛೖΕࢠʹ͢Ε͹ύϫʔΞοϓ ྫ2 ୈ1ϧʔϓͰશ݅ճ͢ O(n) ୈ2ϧʔϓ΋શ݅ճ͢ O(n)

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ୈҰҾ਺͸࠷େͰ਺ඦ݅ఔ౓͕ͩͬͨ ୈೋҾ਺ͷσʔλ਺͕੒௕͍ͯͬͯ͠… ྫ2 ୈ1ϧʔϓͰશ݅ճ͢ O(n) ୈ2ϧʔϓ΋શ݅ճ͢ O(n)

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ྫ2ͷΞϧΰϦζϜΛ࡞ͬͯ ࣮ଌͯ͠ΈΔ

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σʔλྔʹΑΔੑೳͷྼԽ ॲཧ࣌ؒ(ඵ) σʔλ݅਺ (ୈ1,2 Ҿ਺ಉ͡)

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ͪΌΜͱO(n^2)ͷ άϥϑʹͳͬͨ

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ࣄલʹݕ஌Ͱ͖ͳ͍͔ʁ

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࣮͸ྫ̍ɾ̎ͷίʔυ͸ ୯ମςετ -> ௨ա ड͚ೖΕςετ -> ௨ա ௨աͯ͠͠·͍ͬͯͨ…

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ෛՙςετ ίʔυϨϏϡʔ ࣄલݕग़Մೳͳࡆ

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ෛՙςετ σʔλྔ͕ലେʹͳΔ͜ͱ͕ Θ͔͍ͬͯΔϓϩμΫτ͸ߦ͍ͬͯΔɻ ௨ৗͷϓϩμΫτͩͱ ͋Μ·Γ΍ͬͯΔͷݟͨ͜ͱແ͍ɻ

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ίʔυϨϏϡʔ ϨϏϡΞʔͷεΩϧ΍ܦݧʹґଘ ࣄલʹܭࢉྔʹ͍ͭͯ νʔϜ಺Ͱษڧձͱ͔ͯ͠Ε͹ ࢦఠˍमਖ਼͸؆୯ͩͱࢥ͏

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؂ࢹπʔϧͰɺॲཧ࣌ؒͷϝτϦΫεΛݟͯ ཧ٧ΊͰॲཧ࣌ؒͷ஗͍෦෼ΛಛఆͰ͖Ε͹ ·͋ɺٴୈ఺ͩͱࢥ͏ɻ ࠷ѱݟಀͯ͠΋