392. Is Subsequence #55
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nodchip
reviewed
Aug 17, 2024
| def isSubsequence(self, s: str, t: str) -> bool: | ||
| i = 0 | ||
| for c in t: | ||
| if i == len(s): |
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i == len(s) が重複しているのが気になりました。
for c in t:
if s[i] != c:
continue
i += 1
if i == len(s):
return True
return False
と書くと良いかもしれません。
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その方法だとsが空文字のときを別で考慮しないとIndexErrorになるんですよね、ただ見比べるとご提案いただいた方が素直な気がしました。
| - 空間計算量: O(n) | ||
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| ```py | ||
| class Solution: |
rihib
reviewed
Aug 21, 2024
| 所要時間: 0:47 | ||
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| m: len(s), n: len(t) | ||
| - 時間計算量: 分からない。1文字あたりパターンに対して指数時間かかるとすると O(n * 2^m) か？ |
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Pythonの正規表現エンジンはバックトラッキングを使用しているようなのでその時間計算量と空間計算量で合ってる気はします（僕も確信はないですが）
oda
reviewed
Aug 23, 2024
| def isSubsequence(self, s: str, t: str) -> bool: | ||
| i = -1 | ||
| for c in s: | ||
| i = t.find(c, i + 1) |
nittoco
reviewed
Aug 24, 2024
| char_to_indexes[c].append(i) | ||
| prev_index = -1 | ||
| for c in s: | ||
| indexes = char_to_indexes[c] |
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解き方面白いです。
indexesの生存期間が長いので、indexes_of_cくらいの説明があってもいいかもしれませんが(自分は1回目読んでる時最後の方で忘れた)、好みの範囲かもしれません。
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indexesも使われれますが、indicesという複数形も使われます（元々のラテン語のようです）
matrix -> matrices
index -> indices
などと同じですね。
個人的には教科書などではindicesの方がよく見かける気がしました。
https://stackoverflow.com/questions/1378781/proper-terminology-should-i-say-indexes-or-indices
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https://leetcode.com/problems/is-subsequence/description/