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Gathering Children](https://atcoder.jp/contests/abc136/tasks/abc136_d) | パリティ(偶奇性) | | [ruby](hard/ruby/abc136_d.rb), [kotlin](hard/kotlin/abc136_d.kt) |\n| 2 | [B - Kleene Inversion](https://atcoder.jp/contests/jsc2019-qual/tasks/jsc2019_qual_b) | 転倒数, 繰り返し | | [ruby](hard/ruby/jsc2019_qual_b.rb) |\n| 3 | [A - Range Flip Find Route](https://atcoder.jp/contests/agc043/tasks/agc043_a) | 全探索, DP, 変化点 | | [ruby](hard/ruby/agc043_a.rb) |\n| 4 | [B - Tax Rate](https://atcoder.jp/contests/sumitrust2019/tasks/sumitb2019_b) | 全探索 | | [ruby](hard/ruby/sumitb2019_b.rb) |\n| 5 | [B - Can you solve this?](https://atcoder.jp/contests/abc121/tasks/abc121_b) | 全探索 | | [ruby](hard/ruby/abc121_b.rb) |\n| 6 | [B - Bishop](https://atcoder.jp/contests/panasonic2020/tasks/panasonic2020_b) | パターン, コーナーケースを考慮する | | [ruby](hard/ruby/panasonic2020_b.rb) |\n| 7 | [D - Integer Cards](https://atcoder.jp/contests/abc127/tasks/abc127_d) | 貪欲法 | | [ruby](hard/ruby/abc127_d.rb), [kotlin](hard/kotlin/abc127_d.kt) |\n| 8 | [E - Double Factorial](https://atcoder.jp/contests/abc148/tasks/abc148_e) | | | [ruby](hard/ruby/abc148_e.rb) |\n| 9 | [B - Template Matchin](https://atcoder.jp/contests/abc054/tasks/abc054_b) | | | [ruby](hard/ruby/abc054_b.rb) |\n| 10 | [D - Enough Array](https://atcoder.jp/contests/abc130/tasks/abc130_d) | | | [ruby](hard/ruby/abc130_d.rb) |\n| 11 | [D - Disjoint Set of Common Divisors](https://atcoder.jp/contests/abc142/tasks/abc142_d) | 最大公約数, 素数 | | [ruby](hard/ruby/abc142_d.rb), [kotlin](hard/kotlin/abc142_d.kt) |\n| 12 | [B - Counting of Trees](https://atcoder.jp/contests/nikkei2019-2-qual/tasks/nikkei2019_2_qual_b) | | | [ruby](hard/ruby/nikkei2019_2_qual_b.rb), [kotlin](hard/kotlin/nikkei2019_2_qual_b.kt) |\n| 13 | [D - Lucky PIN](https://atcoder.jp/contests/sumitrust2019/tasks/sumitb2019_d) | 二分探索, 小さい方で考える | | [ruby](hard/ruby/sumitb2019_d.rb), [kotlin](hard/kotlin/sumitb2019_d.kt) |\n| 14 | [C - Digits in Multiplication](https://atcoder.jp/contests/abc057/tasks/abc057_c) | | | [kotlin](hard/kotlin/abc057_c.kt) |\n| 15 | [D - Flipping Signs](https://atcoder.jp/contests/abc125/tasks/abc125_d) | | | [kotlin](hard/kotlin/abc125_d.kt) |\n| 16 | [D - Line++](https://atcoder.jp/contests/abc160/tasks/abc160_d) | | | [kotlin](hard/kotlin/abc160_d.kt) |\n| 17 | [C - AB Substrings](https://atcoder.jp/contests/diverta2019/tasks/diverta2019_c) | | | [kotlin](hard/kotlin/diverta2019_c.kt) |\n| 18 | [C - Back and Forth](https://atcoder.jp/contests/abc051/tasks/abc051_c) | | | [ruby](hard/ruby/abc051_c.rb) |\n| 19 | [D - Grid Coloring](https://atcoder.jp/contests/abc069/tasks/arc080_b) | | | [ruby](hard/ruby/arc080_b.rb) |\n| 20 | [C - ID](https://atcoder.jp/contests/abc113/tasks/abc113_c) | | | [ruby](hard/ruby/abc113_c.rb) |\n| 21 | [D - Binomial Coefficients](https://atcoder.jp/contests/abc094/tasks/arc095_b) | 組み合わせの性質 | | [ruby](hard/ruby/arc095_b.rb) |\n| 22 | [C - String Transformation](https://atcoder.jp/contests/abc110/tasks/abc110_c) | | | [ruby](hard/ruby/abc110_c.rb) |\n| 23 | [C - 白昼夢](https://atcoder.jp/contests/abc049/tasks/arc065_a) | 後ろからマッチ | | [ruby](hard/ruby/arc065_a.rb) |\n| 24 | [B - Robot Arms](https://atcoder.jp/contests/keyence2020/tasks/keyence2020_b) | 貪欲法 | | [ruby](hard/ruby/keyence2020_b.rb) |\n| 25 | [C - Special Trains](https://atcoder.jp/contests/abc084/tasks/abc084_c) | 二分探索法 | | [ruby](hard/ruby/abc084_c.rb) |\n| 26 | [B - K個のケーキ](https://atcoder.jp/contests/code-festival-2016-qualc/tasks/codefestival_2016_qualC_b) | | | [ruby](hard/ruby/codefestival_2016_qualC_b.rb) |\n| 27 | [D - Ki](https://atcoder.jp/contests/abc138/tasks/abc138_d) | 深さ優先探索 | | [ruby](hard/ruby/abc138_d.rb) |\n| 28 | [C - Candles](https://atcoder.jp/contests/abc107/tasks/arc101_a) |  | | [ruby](hard/ruby/abc107_c.rb) |\n| 29 | [B - Colorful Creatures](https://atcoder.jp/contests/agc011/tasks/agc011_b) |  | | [ruby](hard/ruby/agc011_b.rb) |\n| 30 | [A - Getting Difference](https://atcoder.jp/contests/agc018/tasks/agc018_a) | 最大公約数 | | [ruby](hard/ruby/agc018_a.rb) |\n| 31 | [D - Preparing Boxes](https://atcoder.jp/contests/abc134/tasks/abc134_d) | 排他論理和 | | [ruby](hard/ruby/abc134_d.rb) |\n| 32 | [C - Factors of Factorial](https://atcoder.jp/contests/arc067/tasks/arc067_a) | 約数, 素数, 組み合わせ | | [ruby](hard/ruby/arc067_a.rb) |\n| 33 | [D - Rain Flows into Dams](https://atcoder.jp/contests/abc133/tasks/abc133_d) | 周期性, 決め打ち | | [ruby](hard/ruby/abc133_d.rb) |\n| 34 | [C - Lining Up](https://atcoder.jp/contests/arc066/tasks/arc066_a) | 周期性 | | [ruby](hard/ruby/arc066_a.rb) |\n| 35 | [D - Katana Thrower](https://atcoder.jp/contests/abc085/tasks/abc085_d) | 貪欲法 | | [ruby](hard/ruby/abc085_d.rb) |\n| 36 | [A - Triangle](https://atcoder.jp/contests/agc036/tasks/agc036_a) | 三角形の面積(内積), 固定 | | [ruby](hard/ruby/agc036_a.rb) |\n| 37 | [C - Strawberry Cakes](https://atcoder.jp/contests/ddcc2020-qual/tasks/ddcc2020_qual_c) | 埋める | | [ruby](hard/ruby/ddcc2020_qual_c.rb) |\n| 38 | [D - Maze Master](https://atcoder.jp/contests/abc151/tasks/abc151_d) | 幅優先探索 | | [ruby](hard/ruby/abc151_d.rb) |\n| 39 | [C - Stones](https://atcoder.jp/contests/tenka1-2019/tasks/tenka1_2019_c) | 動的計画法 | | [ruby](hard/ruby/tenka1_2019_c.rb) |\n| 40 | [C - Inserting 'x'](https://atcoder.jp/contests/code-festival-2017-qualc/tasks/code_festival_2017_qualc_c) | | | [ruby](hard/ruby/code_festival_2017_qualc_c.rb) |\n| 41 | [C - Triangular Relationshi](https://atcoder.jp/contests/abc108/tasks/arc102_a) | MOD | | [ruby](hard/ruby/arc102_c.rb) |\n| 42 | [D - Insertion](https://atcoder.jp/contests/abc064/tasks/abc064_d) | スタック、キュー | | [ruby](hard/ruby/abc064_d.rb) |\n| 43 | [D - Wall](https://atcoder.jp/contests/abc079/tasks/abc079_d) | Warshall Floyd | | [ruby](hard/ruby/abc079_d.rb) |\n| 44 | [C - HonestOrUnkind2](https://atcoder.jp/contests/abc147/tasks/abc147_c) | BIT全探索 | | [ruby](hard/ruby/abc147_c.rb) |\n| 45 | [D - 2017-like Number](https://atcoder.jp/contests/abc084/tasks/abc084_d) | 素数 | | [ruby](hard/ruby/abc084_d.rb) |\n| 46 | [A - STring](https://atcoder.jp/contests/agc005/tasks/agc005_a) | スタック | | [ruby](hard/ruby/agc005_a.rb) |\n| 47 | [D - Lunlun Number](https://atcoder.jp/contests/abc161/tasks/abc161_d) | キュー | | [ruby](hard/ruby/agc161_d.rb) |\n| 48 | [E - Crested Ibis vs Monster](https://atcoder.jp/contests/abc153/tasks/abc153_e) | 動的計画法 | | [ruby](hard/ruby/abc153_e.rb) |\n| 49 | [D - Bouquet](https://atcoder.jp/contests/abc156/tasks/abc156_d) | 動的計画法 | | [ruby](hard/ruby/abc156_d.rb) |\n| 50 | [D - Grid Repainting](https://atcoder.jp/contests/abc088/tasks/abc088_d) | 幅優先探索 | | [ruby](hard/ruby/abc088_d.rb) |\n| 51 | [D - Knight](https://atcoder.jp/contests/abc145/tasks/abc145_d) | 逆元 | | [ruby](hard/ruby/abc145_d.rb) |\n| 52 | [D - Partition](https://atcoder.jp/contests/abc112/tasks/abc112_d) | | | [ruby](hard/ruby/abc112_d.rb) |\n| 53 | [B - Picking Up](https://atcoder.jp/contests/diverta2019-2/tasks/diverta2019_2_b) | | | [ruby](hard/ruby/diverta2019_2_b.rb) |\n| 54 | [E - Red and Green Apples](https://atcoder.jp/contests/abc160/tasks/abc160_e) | 貪欲法 | | [ruby](hard/ruby/abc160_e.rb) |\n| 55 | [D - Walk and Teleport](https://atcoder.jp/contests/abc052/tasks/arc067_b) | 動的計画法 | | [ruby](hard/ruby/abc052_d.rb) |\n| 56 | [B - Two Arrays](https://atcoder.jp/contests/apc001/tasks/apc001_b) | | | [ruby](hard/ruby/apc001_b.rb) |\n| 57 | [A - Zero-Sum Ranges](https://atcoder.jp/contests/agc023/tasks/agc023_a) | 累積和 | | [ruby](hard/ruby/agc023_a.rb) |\n| 58 | [D - DivRem Number](https://atcoder.jp/contests/diverta2019/tasks/diverta2019_d) | 約数 | | [ruby](hard/ruby/diverta2019_d.rb) |\n| 59 | [C - 755](https://atcoder.jp/contests/abc114/tasks/abc114_c) | 全探索, 深さ優先探索 | | [ruby](hard/ruby/abc114_c.rb) |\n| 60 | [D - Handstand 2](https://atcoder.jp/contests/abc152/tasks/abc152_d) | 全探索, 動的計画法 | | [ruby](hard/ruby/abc152_d.rb) |\n| 61 | [C - Next Letter](https://atcoder.jp/contests/code-festival-2016-quala/tasks/codefestival_2016_qualA_c) | 貪欲法 | | [ruby](hard/ruby/codefestival_2016_qualA_c.rb) |\n| 62 | [D - Lamp](https://atcoder.jp/contests/abc129/tasks/abc129_d) | bytes | | [ruby](hard/ruby/abc129_d.rb) |\n| 63 | [C. Iroha's Obsession](https://atcoder.jp/contests/arc058/tasks/arc058_a) | | | [ruby](hard/ruby/arc058_a.rb) |\n| 64 | [C - Bridge](https://atcoder.jp/contests/abc075/tasks/abc075_c) | Low Link, 二重辺連結成分分解 | | [ruby](hard/ruby/abc075_c.rb) |\n| 65 | [D - Card Eater](https://atcoder.jp/contests/abc053/tasks/arc068_b) | | | [ruby](hard/ruby/abc053_d.rb) |\n| 66 | [B - ABC](https://atcoder.jp/contests/agc034/tasks/agc034_b) | 転倒数 | | [ruby](hard/ruby/abc034_b.rb) |\n| 67 | [D - Christmas](https://atcoder.jp/contests/abc115/tasks/abc115_d) | 深さ優先探索 | | [ruby](hard/ruby/abc115_d.rb) |\n| 68 | [D - String Equivalence](https://atcoder.jp/contests/panasonic2020/tasks/panasonic2020_d) | 深さ優先探索 | | [ruby](hard/ruby/panasonic2020_d.rb) |\n| 69 | [C - Align](https://atcoder.jp/contests/tenka1-2018/tasks/tenka1_2018_c) | パターンの考察 | | [ruby](hard/ruby/tenka1_2018_c.rb) |\n| 70 | [C - Snuke Festival](https://atcoder.jp/contests/abc077/tasks/arc084_a) | 二分探索法, 真ん中から考える | | [ruby](hard/ruby/abc077_c.rb) |\n| 71 | [C - Linear Approximation](https://atcoder.jp/contests/abc102/tasks/arc100_a) | 差の絶対値の総和は中央値を使う | | [ruby](hard/ruby/abc102_c.rb) |\n| 72 | [C - 4/N](https://atcoder.jp/contests/tenka1-2017/tasks/tenka1_2017_c) |  | | [ruby](hard/ruby/tenka1_2017_c.rb) |\n| 73 | [C - Strange Bank](https://atcoder.jp/contests/abc099/tasks/abc099_c) | 動的計画法 | | [ruby](hard/ruby/abc099_c.rb) |\n| 74 | [D - Harlequin](https://atcoder.jp/contests/caddi2018b/tasks/caddi2018_b) | ゲーム | | [ruby](hard/ruby/caddi2018b_d.rb) |\n| 75 | [D - Face Produces Unhappiness](https://atcoder.jp/contests/abc140/tasks/abc140_d) | ランレングス圧縮, 変化点は2箇所 | | [ruby](hard/ruby/abc140_d.rb) |\n| 76 | [C. Many Formulas](https://atcoder.jp/contests/abc045/tasks/arc061_a) | ビット全探索 | | [ruby](hard/ruby/abc045_c.rb) |\n| 77 | [A - 01 Matrix](https://atcoder.jp/contests/agc038/tasks/agc038_a) | 数学的考察 | | [ruby](hard/ruby/agc038_a.rb) |\n| 78 | [C - K-th Substring](https://atcoder.jp/contests/abc097/tasks/arc097_a) | 辞書順 | | [ruby](hard/ruby/abc097_c.rb) |\n| 79 | [D - Handstand](https://atcoder.jp/contests/abc124/tasks/abc124_d) | 尺取法, 累積和 | | [ruby](hard/ruby/abc124_d.rb) |\n| 80 | [D - Remainder Reminder](https://atcoder.jp/contests/abc090/tasks/arc091_b) | | | [ruby](hard/ruby/abc090_d.rb) |\n| 81 | [C - Boxes and Candies](https://atcoder.jp/contests/abc048/tasks/arc064_a) | 貪欲法 | | [ruby](hard/ruby/abc048_c.rb) |\n| 82 | [C - Different Strokes](https://atcoder.jp/contests/nikkei2019-qual/tasks/nikkei2019_qual_c) | 貪欲法 | | [ruby](hard/ruby/nikkei2019-qual_c.rb) |\n| 83 | [A - Darker and Darker](https://atcoder.jp/contests/agc033/tasks/agc033_a) | 幅優先探索 | | [ruby](hard/ruby/agc033_a.rb) |\n| 84 | [C - Shopping Street](https://atcoder.jp/contests/abc080/tasks/abc080_c) | BIT全探索 | | [ruby](hard/ruby/abc080_c.rb) |\n| 85 | [C - Pyramid](https://atcoder.jp/contests/abc112/tasks/abc112_c) | 全探索 | | [ruby](hard/ruby/abc112_c.rb) |\n| 86 | [D - Coloring Dominoes](https://atcoder.jp/contests/abc071/tasks/arc081_b) | パターン列挙 | | [ruby](hard/ruby/abc071_d.rb) |\n| 87 | [D - Friend Suggestions](https://atcoder.jp/contests/abc157/tasks/abc157_d) | Union Find | | [ruby](hard/ruby/abc157_d.rb) |\n| 88 | [D - XOR World](https://atcoder.jp/contests/abc121/tasks/abc121_d) | XOR | | [ruby](hard/ruby/abc121_d.rb) |\n| 89 | [E - Colorful Hats 2](https://atcoder.jp/contests/sumitrust2019/tasks/sumitb2019_e) | DP | | [ruby](hard/ruby/sumitb2019_e.rb) |\n| 90 | [D - Even Relation](https://atcoder.jp/contests/abc126/tasks/abc126_d) | 法則性, DP, 偶奇 | | [ruby](hard/ruby/abc126_d.rb) |\n| 91 | [D - Coloring Edges on Tree](https://atcoder.jp/contests/abc146/tasks/abc146_d) | 深さ優先探索, MEX | | [ruby](hard/ruby/abc146_d.rb) |\n| 92 | [B - Unplanned Queries](https://atcoder.jp/contests/agc014/tasks/agc014_b) | 木 | | [ruby](hard/ruby/agc014_b.rb) |\n| 93 | [D - Transit Tree Path](https://atcoder.jp/contests/abc070/tasks/abc070_d) | ダイクストラ法 | | [ruby](hard/ruby/abc070_d.rb) |\n| 94 | [D - Blue and Red Balls](https://atcoder.jp/contests/abc132/tasks/abc132_d) | フェルマーの小定理, 組み合わせ | | [ruby](hard/ruby/abc0132_d.rb) |\n| 95 | [D - Xor Sum 4](https://atcoder.jp/contests/abc147/tasks/abc147_d) | フェルマーの小定理, 組み合わせ | | [ruby](hard/ruby/abc147_d.rb) |\n| 96 | [D - Make Them Even](https://atcoder.jp/contests/abc109/tasks/abc109_d) | 力技 | | [ruby](hard/ruby/abc109_d.rb) |\n| 97 | [C - Base -2 Number](https://atcoder.jp/contests/abc105/tasks/abc105_c) | 二進数 | | [ruby](hard/ruby/abc105_c.rb) |\n| 98 | [C - Palindromic Matrix](https://atcoder.jp/contests/code-festival-2017-quala/tasks/code_festival_2017_quala_c) | 法則性 | | [ruby](hard/ruby/code-festival-2017-quala_c.rb) |\n| 99 | [B - Simplified mahjong](https://atcoder.jp/contests/agc003/tasks/agc003_b) | 貪欲法 | | [ruby](hard/ruby/agc003_b.rb) |\n| 100 | [C - Vacant Seat](https://atcoder.jp/contests/apc001/tasks/apc001_c) | 二分探索法 | | [ruby](hard/ruby/apc001_c.rb) |\n","project_url":"https://awesome.ecosyste.ms/api/v1/projects/github.com%2Ffumtas1k%2Fatcoder_problems","html_url":"https://awesome.ecosyste.ms/projects/github.com%2Ffumtas1k%2Fatcoder_problems","lists_url":"https://awesome.ecosyste.ms/api/v1/projects/github.com%2Ffumtas1k%2Fatcoder_problems/lists"}