Question

基本上，程序向用户询问（X，Y，Z）坐标的范围，并询问他希望生成的点数。这些值将传递给对象类，在该对象类中进行快速排序算法。一旦将值传递给writeData类，它们就会继续在文件中打印一个示例输出：其中点数是2（2组xyz坐标）范围是1（从正无穷大到负无穷大）

(0.01916820621893911),(0.7031915303569696),(0.8313160912583086)
(-0.9343528090486088),(0.015998642441189093),(0.49980249751031924)

正如您可以通过输出判断的那样，它根本没有排序，如果我的算法似乎有效，为什么会出现此问题。我在过去一小时左右尝试过调试，但无济于事。此外，由于快速排序mufti维数组并不经常使用，这是我可以尝试使用的唯一算法。无论如何，一些或任何输入将帮助我解决这个难题！

主要节目（短而甜）：

import java.io.*;
public class test {
  public static void main (String [] args) throws IOException {
  BufferedReader myInput = new BufferedReader (new InputStreamReader (System.in));

  testplus1 c = new testplus1();
  double dataPoints [][] = new double [3][10000];
  int numPoints;
  int range;
  String input;

  System.out.println("Please enter a range");
  input = myInput.readLine();
  range = Integer.parseInt(input);
  System.out.println("Please enter the number of points");
  input = myInput.readLine();
  numPoints = Integer.parseInt(input);
  c.setNumPoints(numPoints);
  c.setArray(dataPoints);
  c.setRange(range);

  c.fillArray(dataPoints,range,numPoints);
  } 
}

对象类

import java.io.*;

public class testplus1 {
  private static double [][] myDataPoints;
  private static double [][] sd;
  private static int myRange;
  private static int myNumPoints;

  public testplus1() throws IOException{
    myNumPoints = getNumPoints();
    myRange = getRange();
    myDataPoints = getArray();
    fillArray(myDataPoints,myRange,myNumPoints);
  }

  public void fillArray(double [][] myDataPoints,int myRange, int myNumPoints) throws IOException{
     for(int i = 0; i < myNumPoints; i++) {
      myDataPoints[0][i] =  2* (double)(Math.random () * myRange) - myRange; 
      myDataPoints[1][i] =  2* (double)(Math.random () * myRange) - myRange; 
      myDataPoints[2][i] =  2* (double)(Math.random () * myRange) - myRange; 
     sort(myDataPoints,0,0,myDataPoints.length-1);
     }
  }

 public double[][] sort(double[][] array, int key, int down, int top) throws IOException{
      double[][] a = new double[array.length][3];
      System.arraycopy(array,0,a,0, a.length);

       int i = down;
       int j = top;

       double x = a[(down + top) / 2][key];

        do {
            while (a[i][key] < x) {
                i++;
            }

            while (a[j][key] > x) {
                j--;
            }

            if (i <= j) {
                double[] temp = new double[a[i].length];

                for (int y = 0; y < a[i].length; y++) {
                    temp[y] = a[i][y];
                    a[i][y] = a[j][y];
                    a[j][y] = temp[y];
                }

                i++;
                j--;
            }
        } while (i <= j);

        if (down < j) {
            a = sort(a, key, down, j);
        }

        if (i < top) {
            a = sort(a, key, i, top);
        }
        writeData(myDataPoints);
        return a;

 }
  public static void writeData(double [][] myDataPoints) throws IOException {
    PrintWriter printWriter = (new PrintWriter ("test123"));
    for(int i = 0; i < myNumPoints; i++) {
      printWriter.println("(" + myDataPoints[0][i] + "),(" + myDataPoints[1][i] + "),(" + myDataPoints[2][i] + ")"); 
    }
    printWriter.close();
  }  

  public void setArray(double [][] dataPoints) {
    myDataPoints = dataPoints;
  }

  public double [][] getArray() {
    return myDataPoints;
  }

  public  void setNumPoints(int numPoints) {
    myNumPoints = numPoints;
  }

  public  int getNumPoints() {
    return myNumPoints; 
  }

  public void setRange(int range) {
    myRange = range; 
  }

  public int getRange() {
    return myRange; 
  }
}

Answer 1

查看您的sort方法。

public double[][] sort(double[][] array, int key, int down, int top) throws IOException{
    double[][] a = new double[array.length][3];
    System.arraycopy(array,0,a,0, a.length);

您创建一个新数组a并对其执行所有操作而不是原始输入数组（对原始数组的更改将在方法外自动显示）。最后，您返回a，这将有效，但在fillArray ...

sort(myDataPoints,0,0,myDataPoints.length-1);

您不会将其分配给任何变量。唯一可以改变的是myDataPoints的副本，而不是mydataPoints本身。

Answer 2

您应该使用Arrays.sort。使用myDataPoints作为第一个参数，使用自定义比较器作为第二个参数。有关详细信息，请查看http://docs.oracle.com/javase/7/docs/api/java/util/Arrays.html#sort(T[], java.util.Comparator)处的文档。

如果您向我提供有关如何对值进行排序的更多信息，我可以举例说明比较器。

为什么这种快速排序根本不起作用？

2 个答案: