Subarray sum equals k #29
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nodchip
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Jun 14, 2024
| class Solution: | ||
| def subarraySum(self, nums: List[int], k: int) -> int: | ||
| cumulative_sum = [0] * (len(nums) + 1) | ||
| cumulative_sum_to_index = defaultdict(list) |
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index が複数格納されるため、 cumulative_sum_to_indexes または cumulative_sum_to_indicies としたほうが良いと思います。
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| count = 0 | ||
| for i in range(len(nums) + 1): | ||
| for j in cumulative_sum_to_index[cumulative_sum[i] - k]: |
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bisect で高速化できるとは思います。ですが、 phase2 の解法が正着のように思いますので、あまりこだわらなくても良いかもしれません。
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あ, なるほど, 単調に増加するloop内部でcumulative_sum_to_index[cumulative_sum[i]]にappendされているのでsortされた状態になっているんですね
oda
reviewed
Jun 15, 2024
| hayashi-ay: https://github.com/hayashi-ay/leetcode/pull/31/files | ||
| Exzrgs: https://github.com/Exzrgs/LeetCode/commit/caa03ede122e5e1d2de4b8ebd24ee26aaf3d743b | ||
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| なんか前も先にindexを保存しておくかfor文の中で動的に処理するかみたいなので先にindexを保存したせいで沼にハマった問題をやった記憶があるな...? |
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maximum subarrayなども確かに同じ類ですね.....累積和だなと思ってそのまま書いたあとワンテンポ置いて動的に処理することで効率化できないか考えるようにでもしてみます
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問題
560. Subarray Sum Equals K