import java.io.BufferedReader;import java.io.FileReader;import java.io.InputStreamReader;import java.io.IOException;import java.util.ArrayList;import java.util.Arrays;import java.util.List;/** * 單詞搜索迷宮 *  * */public class WordSearch{ /** * 在構造函數中構造兩個輸入流，單詞的輸入流，和表格的輸入流 * */  public WordSearch( ) throws IOException  {    puzzleStream = openFile( "輸入表格文件路徑：" );    wordStream  = openFile( "輸入單詞文件路徑：" );    System.out.println( "文件讀取中..." );    readPuzzle( );    readWords( );  }  /**   * @return matches 共有多少個單詞匹配   * 按照每個位置從八個方向搜索   * rd 表示行上得增量，eg:rd=-1，表示向上一行   * cd 表示列上得增量  eg:cd=-1。表示向左一步   * 所以rd=1,cd=0表示南   * rd=-1,cd=0表示北，   * rd=-1,cd=1,表示東北   */  public int solvePuzzle( )  {    int matches = 0;    for( int r = 0; r < rows; r++ )      for( int c = 0; c < columns; c++ )        for( int rd = -1; rd <= 1; rd++ )          for( int cd = -1; cd <= 1; cd++ )            if( rd != 0 || cd != 0 )             matches += solveDirection( r, c, rd, cd );    return matches;  }  /**   * 在指定的坐標上，按照給定的方向搜索，返回匹配的單詞數量   * @return number of matches   */  private int solveDirection( int baseRow, int baseCol, int rowDelta, int colDelta )  {    String charSequence = "";    int numMatches = 0;    int searchResult;    charSequence += theBoard[ baseRow ][ baseCol ];    for( int i = baseRow + rowDelta, j = baseCol + colDelta;         i >= 0 && j >= 0 && i < rows && j < columns;         i += rowDelta, j += colDelta )    {      charSequence += theBoard[ i ][ j ];      searchResult = prefixSearch( theWords, charSequence );      /**       * 下面的 if( searchResult == theWords.length )       * 必須要判斷，否則會出現越界的危險，及當最后一個單詞之匹配前綴時，返回的是索引-1       * */      if( searchResult == theWords.length )        break;      /**       * 如果沒有響應的前綴，直接跳過這個基點的搜索，即使繼續搜索，做的也是無用功       * */      if( !theWords[ searchResult ].startsWith( charSequence ) )        break;      if( theWords[ searchResult ].equals( charSequence ) )      {        numMatches++;        System.out.println( "發現了 " + charSequence + " 在 " +                  baseRow+1 + "行  " + baseCol + " 列   " +                  i + " " + j );      }    }    return numMatches;  }  /**   * 先解釋Arrays.binarySearch(Object[] ,Object)   * 使用二進制搜索算法來搜索指定數組，以獲得指定對象。在進行此調用之前，   * 必須根據數組元素的自然順序 對數組進行升序排序（通過上面的 Sort(Object[] 方法）。   * 如果沒有對數組進行排序，則結果是不明確的。（如果數組包含不可相互比較的元素（例如，字符串和整數），   * 則無法 根據數組元素的自然順序對數組進行排序，因此結果是不明確的。）   * 如果數組包含多個等于指定對象的元素，則無法保證找到的是哪一個。    */  private static int prefixSearch( String [ ] a, String x )  {    int idx = Arrays.binarySearch( a, x );    if( idx < 0 )      return -idx - 1;    else      return idx;  }  /**   * 讀取文件內容，獲得輸入流   */  private BufferedReader openFile( String message )  {    String fileName = "";    FileReader theFile;    BufferedReader fileIn = null;    do    {      System.out.println( message + ": " );      try      {        fileName = in.readLine( );        if( fileName == null )           System.exit( 0 );        theFile = new FileReader( fileName );        fileIn = new BufferedReader( theFile );      }      catch( IOException e )       { System.err.println( "Cannot open " + fileName ); }    } while( fileIn == null );    System.out.println( "Opened " + fileName );    return fileIn;  }  /**   * 讀入表格   * */  private void readPuzzle( ) throws IOException  {    String oneLine;    List<String> puzzleLines = new ArrayList<String>( );    if( ( oneLine = puzzleStream.readLine( ) ) == null )      throw new IOException( "No lines in puzzle file" );    columns = oneLine.length( );    puzzleLines.add( oneLine );    while( ( oneLine = puzzleStream.readLine( ) ) != null )    {      if( oneLine.length( ) != columns )        System.err.println( "Puzzle is not rectangular; skipping row" );      else       puzzleLines.add( oneLine );    }    rows = puzzleLines.size( );    theBoard = new char[ rows ][ columns ];    int r = 0;    for( String theLine : puzzleLines )      theBoard[ r++ ] = theLine.toCharArray( );  }  /**   * 讀取已經按照字典排序的單詞列表   */  private void readWords( ) throws IOException  {    List<String> words = new ArrayList<String>( );    String lastWord = null;    String thisWord;    while( ( thisWord = wordStream.readLine( ) ) != null )    {      if( lastWord != null && thisWord.compareTo( lastWord ) < 0 )      {        System.err.println( "沒有按照字典順序排序，此次跳過" );        continue;      }      words.add( thisWord.trim() );      lastWord = thisWord;    }    theWords = new String[ words.size( ) ]; theWords = words.toArray( theWords );  }   // Cheap main  public static void main( String [ ] args )  {    WordSearch p = null;    try    {      p = new WordSearch( );    }    catch( IOException e )    {      System.out.println( "IO Error: " );      e.printStackTrace( );      return;    }    System.out.println( "正在搜索..." );    p.solvePuzzle( );  }  private int rows;  private int columns;  private char [ ][ ] theBoard;  private String [ ] theWords;  private BufferedReader puzzleStream;  private BufferedReader wordStream;  private BufferedReader in = new BufferedReader( new InputStreamReader( System.in ) );}