如何有效地从字符串中间修剪选定的字符？

Question

谁能想到一种有效的方法（时间明智）从字符串中间修剪几个选定的字符？

我想出的最好的是：

public static string Trim(this string word, IEnumerable<char> selectedChars)
{
    string result = word;
    foreach (char c in selectedChars)
        result = result.Replace(c.ToString(), "");
    return result;
}

但是还是太慢了。

Answer 1

两个选项 spring 要记住：

• 使用 StringBuilder
• 使用正则表达式

这是StringBuilder版本：

public static string Trim(this string word, IEnumerable<char> selectedChars)
{
    // The best form for this will depend largely on the size of selectedChars
    // If you can change how you call the method, there are optimisations you
    // could do here
    HashSet<char> charSet = new HashSet<char>(selectedChars);

    // Give enough capacity for the whole word. Could be too much,
    // but definitely won't be too little
    StringBuilder builder = new StringBuilder(word.Length);

    foreach (char c in word)
    {
        if (!charSet.Contains(c))
        {
            builder.Append(c);
        }
    }
    return builder.ToString();
}

如果您有一组要修剪的固定字符，并且可以一次构建正则表达式，则正则表达式选项可能非常有效。

就像是：

// Put this statically somewhere
Regex unwantedChars = new Regex("[def]", RegexOptions.Compiled);

// Then do this every time you need to use it:
word = unwantedChars.Replace(word, "");

Answer 2

首先使用 StringBuilder 而不是字符串进行替换...
见http://blogs.msdn.com/charlie/archive/2006/10/11/Optimizing-C_2300_-String-Performance.aspx