【转】关键字过滤算法

 

using System;
using System.Collections.Generic;
using System.Text;
using System.Data;
using System.Collections;namespace BLL.Common
{#region 操作类public class KeywordsFilter{#region 关键字过滤/// <summary>/// 关键字过滤/// /// </summary>/// <param name="keywords"></param>/// <returns></returns>public static string Filter(string keywords){//需过滤关键字集合List<string> badwords = new List<string>();KeywordsFilterClass kf = new KeywordsFilterClass();keywords = kf.BadwordInKeywords(keywords, badwords);return keywords;}#endregion}#endregion#region 关键字过滤类/// <summary>/// 关键字过滤类/// </summary>public class KeywordsFilterClass{private Dictionary<string, object> hash = new Dictionary<string, object>();//脏字字典 开头脏字存储private BitArray firstCharCheck = new BitArray(char.MaxValue);//脏字字典 单个char存储private BitArray allCharCheck = new BitArray(char.MaxValue);private int maxLength = 0;/// <summary>/// 初始化 已存储的 过滤字符串/// </summary>/// <param name="words"></param>private void InitHash(List<string> badwords){foreach (string word in badwords){//保存字典内不存在的脏字if (!hash.ContainsKey(word)){hash.Add(word, null);//设置脏字计算长度this.maxLength = Math.Max(this.maxLength, word.Length);firstCharCheck[word[0]] = true;foreach (char c in word){allCharCheck[c] = true;}}}}/// <summary>/// 替换字符串中的脏字为指定的字符/// </summary>/// <param name="text"></param>/// <returns></returns>public string BadwordInKeywords(string text, List<string> badwords){//初始化 脏字字典this.InitHash(badwords);int index = 0;while (index < text.Length){//判断开头脏字if (!firstCharCheck[text[index]]){//未找到开头脏字 则索引累加while (index < text.Length - 1 && !firstCharCheck[text[++index]]) ;}for (int j = 1; j <= Math.Min(maxLength, text.Length - index); j++){if (!allCharCheck[text[index + j - 1]]){break;}string sub = text.Substring(index, j);if (hash.ContainsKey(sub)){text = text.Replace(sub, "**");//this.InitHash(badwords);index += j;break;}}index++;}return text;}}#endregion
}