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naoto-iwase
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| class Solution { | ||
| public: | ||
| int lengthOfLIS(vector<int>& nums) { | ||
| vector<int> subsequence{nums[0]}; |
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問題の制約上ありえないですが、先に空配列を弾いておいてもいいかもしれません。
| - https://github.com/colorbox/leetcode/pull/45/files#diff-9b5a29ecc5f6f85f4ebca7124750d32df099c24d4b0f711e2df2513f6b931a28 | ||
| - lower_boundの返り値が.end()だったら、pushしてそれ以外なら値を更新すれば、もっとシンプルになるな | ||
| - https://github.com/irohafternoon/LeetCode/pull/34/files | ||
| - 変数名はlis_elementsが良さげに感じた。 |
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この変数は、各長さごとのsubsequenceの尻尾の数字を記録し、同じ長さが複数見つかったら値が最小な尻尾を記録するという役割なので、自分ならmin_tailsとし、さらにコメントで、// min_tails[i] is minimum of tail of length i + 1 subsequences とさらに補足します。
他には、マッピングのニュアンスも含めて length_to_min_tail または length_to_min_last_num などのアイデアもあります。
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コメントありがとうございます！
lis_elementsだけじゃ役割がよくわからなかったですね。
変数名だけじゃわかりづらかったら、コメントで補足するようにしていきます。
oda
reviewed
Oct 30, 2025
| - https://github.com/colorbox/leetcode/pull/45/files#diff-9b5a29ecc5f6f85f4ebca7124750d32df099c24d4b0f711e2df2513f6b931a28 | ||
| - lower_boundの返り値が.end()だったら、pushしてそれ以外なら値を更新すれば、もっとシンプルになるな | ||
| - https://github.com/irohafternoon/LeetCode/pull/34/files | ||
| - 変数名はlis_elementsが良さげに感じた。 |
| }; | ||
| ``` | ||
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| - イテレータを使う場合のlower_boundを実装した。 |
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二分探索の cmov (conditional move) を使った最適化というのがあるので、ちょっと見ておいてもいいかもしれません。
https://discord.com/channels/1084280443945353267/1251052599294296114/1265673894917050493
二分探索は分岐予測が当たらないので遅いという性質があるのでそれを避けるための工夫です。
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今回の問題
https://leetcode.com/problems/longest-increasing-subsequence/
次の問題
https://leetcode.com/problems/maximum-subarray/