Java 求二维数组的和

我正在进行一个项目，在这个项目中，我必须读取一个文件并将内容输入到二维数组中。然后我必须求和矩阵的每行、每列和周长。到目前为止，我所有的东西都在工作，除了外围。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相加为等于22。然而，当我把这些列加到总数中时，我得到了32列

代码如下：

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);
    }

   }

import java.util.*；//扫描器类
导入java.io.*；//文件类
公共类Lab10
{
静态公共void main（字符串[]args）引发异常
{    
如果（args.length！=1）
{
println（“错误——用法是：javalab10 matdataN.txt”）；
系统出口（0）；
}
//需求#1：第一个int值：#行，第二个int值：#列
File newFile=新文件（args[0]）；
扫描仪输入=新扫描仪（新文件）；
int numRows=in.nextInt（）；
int numCols=in.nextInt（）；
//要求#2：声明整数的二维数组
int[][]矩阵；
矩阵=新整数[numRows][numCols]；
//要求#3和4：一次读取一行文件（嵌套循环
//和nextInt（））并打印
对于（int i=0；i

如果有人能帮我计算第一列和最后一列的中间值（应该是2+2和8+8），或者如果你有更好的方法来计算周长，我将不胜感激。提前感谢！

//要求#7：遍历周长并求和值，然后显示总和
        //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);

int perTotal=0；
//一线
对于（int j=0；j1）
{
//最后一行
对于（int j=0；j

我建议您这样做：

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);

int perTotal=0；
//上排和下排
for（int c=0；c

以下是您的方法：

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;
}

公共静态int周长（int[][]数组）{
int perimter=0；
对于（int i=0；i

下面是您对所提供阵列的测试：

公共静态void main（字符串[]args）{ println（周长（新的int[][{{1,2,2,3}，{2,4,4,2}，{3,6,3}，{4,8,8,4}））； }

---

输出：42

非常感谢大家！这是一种更简单的方法。仅供参考：我最终做到了

    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);

int perTotal=0；
对于（int i=0；i

在0.4.0版本中有一个（Java线性代数）库处理此任务（目前可在GitHub:上提供，今年夏天将在Maven上提供）。因此，下面是一个简单的示例：

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：la4j的下一版本（0.4.5）支持矩阵和向量的

sum（）

方法：

Matrix a = new Basic2DMatrix(...);
double s = a.sum(); // wrapper around a.fold(...);

只要这样做：

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

    System.out.print(sum);

for（int i=0；iimport 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();
                            }

}


}

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

    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;
    }