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这个数据保存在data.txt中我正在尝试编写一个可以安排的程序

18b0885  // this is the registration number, bullet points to show indentation 
   SS844 Parallel Algorithms        //  These are course taken by student
   SS555 Calculus for Distributed Computing
   SS501 Quantum Communication

17b0585
   SS828 Problem Based Programming
   SS844 Parallel Algorithms 
   SS567 Hacking Quantum Network

17b2582
   SS567 Hacking Quantum Network
   SS844 Parallel Algorithms 
   SS501 Quantum Communication

像这样的一大串数据，需要编写一个程序来缩短这些数据，按注册号升序排列，课程将跟随注册号。所以预期的输出是这样的。

输出遗嘱、课程名称和参加该课程样本的学生注册号：

SS501 Quantum Communication
     18b0885
     17b2582

SS567 Hacking Quantum Network
     17b2582
     17b0585

SS844 Parallel Algorithms 
     17b2582
     17b0585
     18b0885

等等，哪种方法会更容易做到这一点

它没有给出想要的答案

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.FileWriter;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.TreeMap;
import java.util.Set;
import java.util.TreeSet;

public class Sort3 {
  public static void main(String[] args) throws Exception {
    BufferedReader reader = new BufferedReader(new FileReader("data2018.txt"));
    //   Map<String, List<String>> map = new TreeMap<String, List<String>>();
    Map<String, Set<String>> map = new TreeMap<String, Set<String>>();
    String line = reader.readLine();//read header
    while ((line = reader.readLine()) != null) {
      String key = getField(line); // 
      //  List<String> l = map.get(key);
      Set<String> l = map.get(key);
      if (l == null) {
        // l = new LinkedList<String>();
        l = new TreeSet<String>();
        map.put(key, l);
      }
      l.add(line);

    }
    reader.close();
    FileWriter writer = new FileWriter("sorted_numbers4.txt");
    writer.write("");
//     for (List<String> list : map.values()) {
//      for (String val : list) {
//       writer.write(val);
//       writer.write("\n");
//      }
//     }
    for (Set<string> key : map.keySet()){
//print key (subject) here
      writer.write("Subject="+key+"\n");
      for (Set<String> list : map.get(key)) {
        for (String val : list) {
          writer.write(val);
          writer.write("\n");
        }
      }
    }

    writer.close();
  }

  private static String getField(String line) {
    return line.split(",")[0];// 
  }
}

上面的程序输出到另一个像这样的文本文件中

    SS501 Quantum Communication
    SS555 Calculus for Distributed Computing
    SS567 Hacking Quantum Network
    SS567 Hacking Quantum Network
    SS660 Genetic Computation
    SS828 Problem Based Programming
    SS844 Parallel Algorithms
    SS876 Positronics
    SS880 Quark-based Logic

    17b2582
    17b0585
    18b0885

有什么建议可以修改以获得所需的答案吗？

4

1 回答 1

1

代替Map<String, List<String>> map = new TreeMap<String, List<String>>();使用Map<String, Set<String>> map = new TreeMap<String, Set<String>>();，然后使用 aTreeSet代替 a LinkedListegl = new TreeSet<String>();这确保列表（集合）条目是唯一的且已排序。

现在在写出时，首先迭代KeySet，Map然后迭代与每个键关联的值（集合），类似于下面的伪代码：

for (String key : map.keySet()){
//print key (subject) here
writer.write("Subject="+key+"\n");
for (Set<String> list : map.get(key)) {
      for (String val : list) {
       writer.write(val);
       writer.write("\n");
      }
}
}

编辑：从您的示例数据解析逻辑，我可以看到课程名称以“S”字符开头，而注册号是十六进制/数字。可能您可以在解析数据时使用此信息。

于 2013-11-05T05:00:38.307 回答