列对数组进行排序？

user2896120 发表于 Java

用户名

我想对多维数组进行列排序。我已经设置了代码，但是没有显示正确的结果...

排序前的示例：

6.0 4.0 2.0

4.0 2.0 4.0

1.0 3.0 1.0

排序后的示例：

1.0 2.0 1.0

4.0 3.0 2.0

6.0 4.0 4.0

这是我的代码：

  import java.util.Scanner;

    public class ColumnSorting
    {
   public static void main(String [] args)
   {
     run();
   }
   public static void run()
   {
      Scanner input = new Scanner(System.in);
      System.out.print("Please enter the values of your 3x3 matrix: ");
      double[][] matrix = new double[3][3];
      for (int i = 0; i < matrix.length; i++)
      {
         for (int k = 0; k < matrix[i].length; k++)
         {
            matrix[i][k] = input.nextDouble();
         }
      }
      printArrays(matrix);

    }
   public static void printArrays(double[][] matrix)
   {
   System.out.println("Before sorting: ");

       for (int i = 0; i < matrix.length; i++)
      {
        for (int k = 0; k <matrix[i].length; k++)
         {
            System.out.print(matrix[i][k] + " ");
         }
         System.out.println();
      }
    double[][] newMatrix = sortColumns(matrix);
     System.out.println();
    System.out.println("After sorting: ");

    for (int i = 0; i < newMatrix.length; i++)
      {
         for (int j =0; j < newMatrix[i].length; j++)
         {
            System.out.print(newMatrix[i][j] + " ");
         }
         System.out.println();
      }  

   }
   public static double[][] sortColumns(double[][] m)
   {
      double min;
      double temp;
      for (int i = 0; i < 3; i++)
      {
         min = m[0][i];
         for (int k = 0; k < m.length; k++)
         {

            if (min > m[k][i])
            {
               temp = min;
               m[0][i] = m[k][i];
               m[k][i] = temp;
            }
         }
      }
      return m;

   }
}

这就是我得到的：

1.0 3.0 1.0

6.0 4.0 4.0

6.0 4.0 2.0

请告诉我我做错了！

谢谢！

老卡尔金顿

您的排序算法不是排序-它在做奇怪的事情。

这是一个等效的气泡排序演示。

public static double[][] sortColumns(double[][] m) {
    for (int col = 0; col < m[0].length; col++) {
        // Have we swapped one on this pass?
        boolean swapped;
        do {
            swapped = false;
            for (int row = 0; row < m.length - 1; row++) {
                // Should these be swapped?
                if (m[row][col] > m[row + 1][col]) {
                    // Swap this one with the next.
                    double temp = m[row][col];
                    m[row][col] = m[row + 1][col];
                    m[row + 1][col] = temp;
                    // We swapped! Remember to run through again.
                    swapped = true;
                }
            }
        } while (swapped);
    }
    return m;

}

尽管更好的选择是将每一列复制到单独的数组中，然后对其进行排序并放回原位-至少这样一来，您就无需实现自己的排序算法。

public static double[][] sortColumnsProperly(double[][] m) {
    // Sort each colum.
    for (int col = 0; col < m[0].length; col++) {
        // Pull the column out.
        double[] thisCol = new double[m.length];
        for (int i = 0; i < m.length; i++) {
            thisCol[i] = m[i][col];
        }
        // Sort it.
        Arrays.sort(thisCol);
        // Push it back in.
        for (int i = 0; i < m.length; i++) {
            m[i][col] = thisCol[i];
        }
    }
    return m;

}

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