DFA在C#中的实现：过滤敏感词

敏感词、文字过滤是一个网站必不可少的功能，如何设计一个好的、高效的过滤算法是非常有必要的。

在实现文字过滤的算法中，DFA是唯一比较好的实现算法。DFA即Deterministic Finite Automaton，也就是确定有穷自动机，它是是通过event和当前的state得到下一个state，即event+state=nextstate。在实现敏感词过滤的算法中，我们必须要减少运算，而DFA在DFA算法中几乎没有什么计算，有的只是状态的转换。

下面看下在c#方法下实现方式

private bool LoadDictionary()
{
var wordList = new List();
if (_memoryLexicon == null)
{
_memoryLexicon = new WordGroup[char.MaxValue];
var words = new SensitiveWordBll().GetAllWords();
if (words == null)
return false;
foreach (string word in words)
{
wordList.Add(word);
var chineseWord = Microsoft.VisualBasic.Strings.StrConv(word,
Microsoft.VisualBasic.VbStrConv.TraditionalChinese, 0);
if (word != chineseWord)
wordList.Add(chineseWord);
}
foreach (var word in wordList)
{
if (word.Length > 0)
{
var group = _memoryLexicon[word[0]];
if (group == null)
{
group = new WordGroup();
_memoryLexicon[word[0]] = group;
}
group.Add(word.Substring(1));
}
}
}
return true;
} 

private bool Check(string blackWord)
{
_wordlenght = 0;
//检测源下一位游标
_nextCursor = _cursor + 1;
var found = false;
var continueCheck = 0;
//遍历词的每一位做匹配
for (var i = 0; i = _sourceText.Length)
{
if (i - 1 =字符串长度 跳出
if (_nextCursor + offset >= _sourceText.Length)
break;
_wordlenght++;
}
else break;
}
if (_nextCursor + offset >= _sourceText.Length)
{
found = false;
break;
}
if (blackWord[i] == _sourceText[_nextCursor + offset])
{
found = true;
continueCheck = 0;
}
else
{
// 匹配不到时尝试继续匹配4个字符
if (continueCheck
3、测试与使用方法
_illegalWords = new List();
if (string.IsNullOrEmpty(sourceText) && string.IsNullOrEmpty(_sourceText))
{
return sourceText;
}
if (!string.IsNullOrEmpty(sourceText))
_sourceText = sourceText;
_cursor = 0;
if (!LoadDictionary())
{
return _sourceText;
}
var tempString = _sourceText.ToCharArray();
var sourceTextDbc = ToDBC(SourceText);
for (var i = 0; i  0)
ssx = ssx.Replace(word, "*".PadLeft(word.Length, '*'));
}
var datetime2x = DateTime.Now;
var millisecondx = (datetime2x - datetimex).TotalMilliseconds;
Console.WriteLine(millisecondx);
Console.WriteLine(ssx);