一個有限狀態機

有限狀態機和上下文無關文法是相對應的，其在很多場合都很有用途。

寫了一個識別<p>***</p> 的有限狀態機的函數：

功能識別所有的開頭為<p>結尾為</p>，中間為任意字符的字符串。

 

       private void openFileDelInitialFileAndSaveTargetFile(string filePath,int iCount)
        ...{
            try
            ...{
                int count = 0;
                StringBuilder sbToWrite = new StringBuilder();
                StreamReader sr = new StreamReader(filePath, System.Text.Encoding.Default);
                for (int i = 0; i < 4; i++)
                ...{
                    sbToWrite.Append(sr.ReadLine());
                    sbToWrite.Append(" ");
                    count++;
                }
                string content = sr.ReadToEnd();
                sr.Close();
                
         ==識別用的有限狀態機 ==#region ==識別用的有限狀態機 ==
                Stack finateState = new Stack();

                int iStart = 0;
                int iStop = 0;
                int z = 0;
                foreach (char c in content)
                ...{
                    if (c == '<' && finateState.Count == 0)
                    ...{
                        iStart = z;
                        finateState.Push(c);
                        z++;
                        continue;
                    }
                    if( (c == 'p'|| c=='P') && finateState.Count == 1)
    ...{
                        finateState.Push(c);
                        z++;
                        continue;
                    }

                    if (finateState.Count == 1)
                    ...{
                        finateState.Pop();
                        z++;
                        continue;
                    }

                    if (c == '>' && finateState.Count == 2)
                    ...{
                        finateState.Push(c);
                        z++;
       continue;
                    }
                    if (finateState.Count == 2)
                    ...{
                        finateState.Clear();
                        z++;
                        continue;
                    }

                    if (c == '<' && finateState.Count == 3)
                    ...{
                        finateState.Push(c);
                        z++;
                        continue;
                    }

                    if (c == '/' && finateState.Count == 4)
        ...{
                        finateState.Push(c);
                        z++;
                        continue;
                    }
                    if (finateState.Count == 4)
                    ...{
                        finateState.Pop();
                        z++;
                        continue;
                    }


                    if( (c == 'p'|| c=='P') && finateState.Count == 5)
                    ...{
                        finateState.Push(c);
                        z++;
                        continue;
                    }
            &nbsp;       if (finateState.Count == 5)
                    ...{
                        finateState.Pop();
                        finateState.Pop();
                        z++;
                        continue;
                    }

                    if (finateState.Count == 6 && c == '>')
                    ...{
                        iStop = z;
                        string tmp = content.Substring(iStart, iStop - iStart+1).Trim();
                        iStart = 0;
                        iStop = 0;
                        sbToWrite.Append(tmp);
                        sbToWrite.Append(" ");
                        finateState.Clear();
                        count++;
             &nbsp;          z++;
                        continue;

                    }
                    if (finateState.Count == 6)
                    ...{
                        finateState.Pop();
                        finateState.Pop();
                        finateState.Pop();
                        z++;
                        continue;
                    }
                    z++;
                }
                #endregion

                File.Delete(filePath);
                if (count > 4)
                ...{
                    int index = filePath.LastIndexOf('.');//dddd:dddf.txt
                    //filePath = filePath.Substring(0, index);
                    //filePath += ".txt";

                    index = filePath.LastIndexOf('\');
                    filePath = filePath.Substring(0, index);
                    filePath += "\"+iCount.ToString() + ".txt";
                    StreamWriter sw = new StreamWriter(filePath, false, Encoding.Default);
                    sw.Write(sbToWrite.ToString());
                    sw.Close();
                }
            }
            catch (Exception e)
            ...{
                Console.Write("Error:when try to weite the target file!");
                Console.Write(e.Message);
            }


        }
    }