位图排序

 

位图排序： 适合数量较多的整数集合排序。

 

原理：  定义位组，如果整数i存在，则将位组的第i位置为1，以记录其存在。然后位组遍历，确定排序。

 

Code: 

　　

 1 import java.io.*;  2 import java.util.*;  3 public class Main {  4     
 5     
 6 public static void main(String[] argc) throws IOException{  7 
 8         Main test = new Main();  9         String largeFileName = "d:\\File_test\\old.txt"; 10         String destlargeFileName = "d:\\File_test\\new.txt"; 11         test.perform(largeFileName, 100, destlargeFileName,true); 12 } 13     
14 
15 private BitSet bits; 16 public void perform( String largeFileName,int total, String destLargeFileName,boolean asc) throws IOException { 17 System.out.println("BitmapSort Started."); 18  long start = System.currentTimeMillis(); 19  bits = new BitSet(total); 20  FileWriter fw=new FileWriter(new File(destLargeFileName)); 21  BufferedWriter  largeOut=new BufferedWriter(fw); 22  File fr = new File(largeFileName); 23  BufferedReader largeIn = new BufferedReader(new FileReader(fr)); 24  
25 // OutputStreamWriter osw=new OutputStreamWriter(fos, "UTF-8"); 26 //BufferedWriter bw=new BufferedWriter(osw);
27  Integer data; 28  int off = 0; 29  try { 30  while (true) { 31  String Data = largeIn.readLine(); 32  if (Data == null) 33  break; 34  data = Integer.parseInt(Data); 35  int v = data; 36  set(v); 37  off++; 38  } 39  largeIn.close(); 40  int size = bits.size(); 41  System.out.println(String.format("lines : %d ,bits : %d", off, size)); 42  if(asc) { 43      for (int i = 0; i < size; i++) { 44      if (get(i)) { 45          largeOut.write(String.valueOf(i)+"\n"); 46          largeOut.write("\t\n"); 47  } 48  } 49  } 50  largeOut.close(); 51  long stop = System.currentTimeMillis(); 52  long elapsed = stop - start; 53  System.out.println(String.format("BitmapSort Completed.elapsed : %dms",elapsed)); 54  } 55  finally { 56  largeIn.close(); 57  largeOut.close(); 58  } 59  } 60 
61 private void set(int i) { 62  bits.set(i); 63  } 64 private boolean get(int v) { 65  return bits.get(v); 66  } 67 }