Permutations #16
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Permutations #16
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fhiyo
reviewed
Aug 13, 2024
| return | ||
| } | ||
| for _, n := range nums { | ||
| if _, ok := inUse[n]; !ok { |
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ここも非再帰の方法で書いているように
if _, ok := inUse[n]; ok {
continue
}
...の方が読みやすい気が個人的にはしました。
Comment on lines
+58
to
+61
| newInUse := make(map[int]struct{}) | ||
| for k, v := range current.inUse { | ||
| newInUse[k] = v | ||
| } |
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newInUse := maps.Clone(current.inUse)と書けるらしいです。 https://pkg.go.dev/[email protected]#Clone
rihib
commented
Aug 13, 2024
| var permutations [][]int | ||
| for { | ||
| permutations = append(permutations, append([]int{}, nums...)) | ||
| i := len(nums) - 2 |
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Next Permutationでも指摘されたがiの使用範囲が広いのでもっとわかりやすい変数名をつけたい
nittoco
reviewed
Aug 20, 2024
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Permutationsを解きました。レビューをお願い致します。
問題：https://leetcode.com/problems/permutations/
言語：Go
パフォーマンス：$O(n * n!)$ （各順列を生成するのは $O(n)$ で、全体で $n!$ 個の順列が生成される）$O(n * n!)$ （各順列の長さは $n$ で、全体で $n!$ 個の順列が生成される）
時間計算量：
空間計算量：
スタックオーバーフローの可能性：
$O(n)$ 。
permuteBacktrackingRecursion関数のスタックの最悪の深さはgenerate関数は引数やローカル変数を持たないので、戻りアドレスやFPが保存されるとしてスタックフレームサイズは20Bほどになり、スタックの深さは最大でlen(nums)であり、今回の制約ではlen(nums)<=6であることから、使用するスタックサイズは120Bほどなので、スタックオーバーフローの可能性はないと言える。辞書順に順列を生成する：
https://en.wikipedia.org/wiki/Permutation#Generation_in_lexicographic_order
https://en.cppreference.com/w/cpp/algorithm/next_permutation
https://docs.python.org/3/library/itertools.html#itertools.permutations
https://github.com/python/cpython/blob/bc264eac3ad14dab748e33b3d714c2674872791f/Modules/itertoolsmodule.c#L2603
すでに解いた方々：
hayashi-ay/leetcode#5
hayashi-ay/leetcode#57
shining-ai/leetcode#50
SuperHotDogCat/coding-interview#12
goto-untrapped/Arai60#16
Mike0121/LeetCode#14
nittoco/leetcode#21
fhiyo/leetcode#50