2

我正在做一个项目，我必须读取文件并将内容输入二维数组。然后我必须对矩阵的每一行、每一列和周长求和。到目前为止，除了外围之外，我已经完成了所有工作。我正在尝试为顶行、底行和两个外部列的中间创建单独的 for 循环。

矩阵文件如下所示：

1 2 3 4 
2 4 6 8 
2 4 6 8 
3 2 3 4

因此，周长加起来应该是 42。现在我可以成功地将第一行和最后一行添加到等于 22。但是，当我将列添加到总数中时，我得到 32。

这是代码：

import java.util.*; // Scanner class
import java.io.*;  // File class

public class Lab10
{
   static public void main( String [ ] args )  throws Exception
   {    
  if ( args.length != 1 )
  {
    System.out.println("Error -- usage is:  java Lab10 matdataN.txt");
    System.exit( 0 );
  }

    //Requirement #1: first int value: # of rows, second int value: # of cols
    File newFile = new File(args[0]); 
    Scanner in = new Scanner(newFile);

    int numRows = in.nextInt();
    int numCols = in.nextInt();

    //Requirement #2: declare two-d array of ints
    int[][] matrix;
    matrix = new int[numRows][numCols];

    //Requirement #3 & 4: read file one line at a time (nested for loops 
        //and nextInt()) and print

    for (int i = 0; i < numRows; i++)
    {
        for (int j = 0; j < numCols; j++)
        {
            matrix[i][j] = in.nextInt();
            System.out.print(matrix[i][j]+ " ");
        }
    System.out.println();
    }

    //Requirement #5: traverse each row and sum the values and display the sums
    int rowTotal = 0;
    for (int i = 0; i < numRows; i++)
    {
        rowTotal = 0;
        for (int j = 0; j < numCols; j++)
        {
            rowTotal += matrix[i][j];
        }
    System.out.println("Sum for row = " + rowTotal);
    }

    //Requirement #6: traverse each column and sum the values and display the sums
    int colTotal = 0;
    for (int i = 0; i < numRows; i++)
    {
        colTotal = 0;
        for (int j = 0; j < numCols; j++)
        {
            colTotal += matrix[j][i];
        }
    System.out.println("Sum for col = " + colTotal);
    }

    //Requirement #7: traverse the perimeter and sum the values and display the sum

    //sum bottom row matrix
    int perTotal = 0;
    for (int i = (numRows-1); i < numRows; i++)
    {
        perTotal = 0;
        for (int j = 0; j < numCols; j++)
        {
            perTotal += matrix[i][j];
        }
    }

    //sum + top row matrix
    for (int i = 0; i < numRows - (numRows-1); i++)
    {
        for (int j = 0; j < numCols; j++)
        {
            perTotal += matrix[i][j];
        }
    System.out.println("Sum of perimeter = " + perTotal);
    }

    // sum + first col middle
    for (int i = 1; i < (numRows-1); i++)
    {
        for (int j = 0; j < numCols - (numCols-1); j++)
        {
            perTotal += matrix[j][i];
        }
    System.out.println("Sum = " + perTotal);
    }

    // sum + last col middle
    for (int i = 1; i < (numRows-1); i++)
    {
        for (int j = (numCols-1); j < numCols; j++)
        {
            perTotal += matrix[j][i];
        }
    System.out.println(perTotal);
    }

   }

如果有人可以帮助我计算第一列和最后一列的中间值（应该是 2+2 和 8+8），我将不胜感激。或者，如果您有更好的方法来找到周长。提前致谢！

4

9 回答 9

2

在 0.4.0 版本中有一个la4j（Java 的线性代数）库来处理这个任务（目前在 GitHub 上可用：https ://github.com/vkostyukov/la4j ，今年夏天将在 Maven 上可用）。所以，这里是一个简短的例子：

Matrix a = new Basic2DMatrix(...); // creates a real matrix

// calculates the sum of '1' row
double d1 = a.foldRow(1, Matrices.asSumAccumulator(0)); 
// calculates the sum of '2' 
double d2 = a.foldColumn(2, Matrices.asSumAccumulator(0));

// the helper class that fetches border elements of matrix
class PerimeterFetcher implements MatrixFunction {

  private int rows;
  private int columns;

  public PerimeterFectcher(int rows, int columns) {
    this.rows = rows;
    this.columns = columns;
  }      

  @Override
  public double evaluate(int i, int j, double value) {
    return i == 0 ? value : j == 0 ? value : (i + 1) == rows ? value
           : (j + 1) == columns ? value : 0;
  }
}

// calculates the perimeter of matrix
double p = a.fold(Matrices.asSumFunctionAccumulator(0, 
                  new PerimeterFetcher(a.rows(), a.columns())));

UPD：下一个版本的 la4j (0.4.5) 支持sum()矩阵和向量的方法：

Matrix a = new Basic2DMatrix(...);
double s = a.sum(); // wrapper around a.fold(...);
于 2013-03-31T13:22:09.530 回答
2

我建议你这样做：

int perTotal = 0;
// top and bottom row
for (int c = 0; c < numCols; c++)
    perTotal += matrix[0][c] + matrix[numRows-1][c];
// left and right column
for (int r = 1; r < numRows-1; r++)
    perTotal += matrix[r][0] + matrix[r][numCols-1];

// output
System.out.println("Perimeter=" + perTotal);
于 2013-03-26T13:54:13.093 回答
2

这是你的方法：

public static int perimeter(int[][] array) {
    int perimter = 0;
    for (int i = 0; i < array[0].length; i++) {
        perimter += array[0][i] + array[array.length - 1][i];
    }
    for (int r = 1; r < array.length - 1; r++) {
        perimter += array[r][0] + array[r][array[0].length - 1];
    }
    return perimter;
}

这是您使用您提供的数组进行的测试：

public static void main(String[] args) { System.out.println(perimeter(new int[][]{{1, 2, 2, 3}, {2, 4, 4, 2}, {3, 6 , 6, 3}, {4, 8, 8, 4}})); }

输出：42

于 2013-03-26T14:14:06.847 回答
1 
        //Requirement #7: traverse the perimeter and sum the values and display the sum

        int perTotal = 0;

        // First line
        for (int j = 0; j < numCols; j++)
        {
            perTotal += matrix[0][j];
        }

        // If there is only one line, then it is done.
        if (numRows > 1)
        {
            // Last line
            for (int j = 0; j < numCols; j++)
            {
                perTotal += matrix[numRows-1][j];
            }

            // Other lines
            for (int i = 1; i < numRows -1); i++)
            {
                perTotal += matrix[i][0] + matrix[i][numcols -1];
            }
        }

    //Perimeter
    System.out.println("Perimter="+perTotal);
于 2013-03-26T13:51:50.280 回答
1

只需这样做： 

        for (int i = 0; i < ROWS; i++){
           for (int j = 0; j < COLUMNS; j++){
             sum = sum + myArray[i][j];
        }
    }

    System.out.print(sum);

这应该给你总和。

于 2017-01-21T04:31:54.700 回答
0

非常感谢大家！这种更简单的方法。仅供参考：我最终做了

    int perTotal = 0;
    for (int i = 0; i < numCols; i++)
    {
        perTotal += matrix[0][i] + matrix[numRows-1][i];
    }
    for (int j = 1; j < numRows-1; j++)
    {
        perTotal += matrix[j][0] + matrix[j][numCols-1];
    }
    System.out.println("Perimeter = " + perTotal);
于 2013-03-26T14:25:38.673 回答
0

您可以简单地使用：

static int sumMultiArray(int[][] array) {
int sum = 0;
for (int[] ints : array) {
    for (int number : ints) {
        sum += number;
    }
}
return sum;

}

于 2019-08-31T19:56:55.360 回答
0

尝试以下操作： 

import java.util.Scanner;
public class TwoDarray {

public static void main(String[] args) 
{
    Scanner scn=new Scanner(System.in);

    System.out.print("Enter the first Rows of Array :");    //Input first Rows and Columns
    int row1 = scn.nextInt();
    System.out.print("Enter the first columns of Array:");
    int col1 = scn.nextInt();
    System.out.print("Enter the second Rows of Array :");   //Input second rows and column
    int row2 = scn.nextInt();
    System.out.print("Enter the second columns of Array:");
    int col2 = scn.nextInt();

    int arr1[][] = new int[row1][col1];                     // Input the elements in first row and column

            System.out.println("Enter the elements in First row and column");
                for(int i=0;i<row1;i++)
                {
                    for(int j=0;j<col1;j++)
                    {
                        arr1[i][j]=scn.nextInt();
                    }
                }

    int arr2[][] = new int[row2][col2];                     // Input the elements in second row and column

        System.out.println("Enter the elements in second row and column");
            for(int i=0;i<row2;i++)
            {
                for(int j=0;j<col2;j++)
                {
                    arr2[i][j]=scn.nextInt();
                }

            }

    System.out.println("Output of first row and column is ");       //output of first row and column
        for(int i=0;i<row1;i++)
        {
            for(int j=0;j<col1;j++)
            {
                System.out.print(arr1[i][j]+" ");
            }   System.out.println();
        }

                System.out.println("output of secound row and column");         //out put of second row and column
                    for(int i=0;i<row2;i++)
                    {
                        for(int j=0;j<col2;j++)
                        {
                            System.out.print(arr2[i][j]+" ");
                        }       System.out.println();
                    }


                                                        //sum of first and second row and column

                    int sum[][] = new int[row1][col1];
                        for(int i=0;i<row1;i++)
                        {
                            for(int j=0;j<col1;j++)
                            {
                                sum[i][j]=arr1[i][j]+arr2[i][j];
                            }
                        }

                        System.out.println("sum of two matrix output");         //sum of two matrix output
                            for(int i=0;i<row1;i++)
                            {
                                for(int j=0;j<col1;j++)
                                {
                                    System.out.print(sum[i][j]+" ");
                                }       System.out.println();
                            }

}


}
于 2017-08-07T09:00:36.877 回答
0 
    private static int sumElementInArray(int[][] arrayWithElement) {
        int sum = 0;
        for (int i = 0; i < arrayWithElement.length; i++) {
            sum += IntStream.of(arrayWithElement[i]).sum();
        }
        return sum;
    }
于 2021-04-15T02:17:50.227 回答