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Backspace String Compare #43

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Backspace String Compare #43

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rihib
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@rihib rihib commented Oct 15, 2024

Backspace String Compareを解きました。レビューをお願い致します。

問題:https://leetcode.com/problems/backspace-string-compare/
言語:Go

すでに解いている方々:
Kitaken0107/GrindEasy#21

後ろから見ていく方法は追加の空間が必要なくなるが、実装が複雑になる。
個人的には必要がなければできるだけスタックを使ってシンプルに実装する方が良いと思っている。
*/
func backspaceCompareStep1(s string, t string) bool {
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この解法が一番シンプルに感じました。

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@oda oda Oct 16, 2024

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これが一番いいように思いますね。変わったことをしたいならば Goroutine はどうですか。

func iterateReverse(s []rune, c chan rune) {
    defer close(c)
    backspaceCount := 0
    for i := len(s) - 1; i >= 0; i-- {
        if s[i] == '#' {
            backspaceCount++
        } else if backspaceCount > 0 {
            backspaceCount--
        } else {
            c <- s[i]
        }
    }
}

func backspaceCompare(s string, t string) bool {
    cs := make(chan rune)
    ct := make(chan rune)
    go iterateReverse([]rune(s), cs)
    go iterateReverse([]rune(t), ct)
    for vs := range cs {
        vt, ok := <-ct
        if !ok || vs != vt {
            return false
        }
    }
    if _, ok := <-ct; ok {
        return false
    }   
    return true
}```

i, j := len(runeS)-1, len(runeT)-1
for i >= 0 || j >= 0 {
i, j = nextIndex(runeS, i), nextIndex(runeT, j)
if i >= 0 && j >= 0 && runeS[i] == runeT[j] {
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i >= 0 && j >= 0 が 2 回登場しているなど、ループ内の処理の流れの見通しが悪く感じました。処理の順番を変えたほうがすっきりすると思います。

自分は Go 言語を書けないため、 C++ で書きますが、

class Solution {
public:
    bool backspaceCompare(string s, string t) {
        int s_index = ProcessBackspace(s.size() - 1, s);
        int t_index = ProcessBackspace(t.size() - 1, t);
        while (s_index >= 0 && t_index >= 0) {
            if (s[s_index] != t[t_index]) {
                return false;
            }
            s_index = ProcessBackspace(s_index - 1, s);
            t_index = ProcessBackspace(t_index - 1, t);
        }
        return s_index < 0 && t_index < 0;
    }

    int ProcessBackspace(int index, const string& s) {
        int num_backspaces = 0;
        while (index >= 0) {
            if (s[index] == '#') {
                ++num_backspaces;
                --index;
                continue;
            }

            if (num_backspaces > 0) {
                --num_backspaces;
                --index;
                continue;
            }

            break;
        }
        return index;
    }
};

はいかがでしょうか?

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3 participants