387. First Unique Character in a String#15
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tom4649
reviewed
Mar 27, 2026
| ```Python3 | ||
| class Solution: | ||
| def firstUniqChar(self, s: str) -> int: | ||
| unique_char_poisitions = {} |
| - v3.7以降から、辞書の順番は挿入順になるため、自分の案2で行っていたソートは不要 | ||
| - https://docs.python.org/3/library/stdtypes.html#dict | ||
| - > Changed in version 3.7: Dictionary order is guaranteed to be insertion order. | ||
| - OrderedDictを使っても、辞書の順番は挿入順になる |
nodchip
reviewed
Mar 29, 2026
| ```Python3 | ||
| class Solution: | ||
| def firstUniqChar(self, s: str) -> int: | ||
| char_position = defaultdict(list) |
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この用途であれば、 collections.Counter も有用だと思います。
https://docs.python.org/3/library/collections.html#collections.Counter
| for i, char in enumerate(s): | ||
| char_position[char].append(i) | ||
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| first_unique_positions = [v[0] for k, v in char_position.items() if len(v) == 1] |
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この方針で書くのであれば、 for 文で先頭から回し、 len(v) == 1 のものを return すると、シンプルかつ速くなるかもしれません。
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この問題: First Unique Character in a String
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