计算矩阵中每一列的总和将为每一列返回相同的结果 [英] Computing the sum of each column in a matrix returns the same result for every column

问题描述

这应该将每一列的所有元素相加并给出每个元素的总和.当我运行它时，它只为每列给出相同的答案.我想念什么吗?

This is supposed to add up all elements of each column and give the sum for each. When I run it, it just gives the same answer for each column. Am I missing something?

    import java.util.Scanner;

public class SumColumnElements {
  public static void main(String[] args) {
    double[][] matrix = new double [3][4];

    Scanner input = new Scanner(System.in);
    System.out.println("Enter " + matrix.length + " rows and " + matrix[0].length + " columns:");
    for (int row = 0;row < matrix.length; row++) {
      for (int column = 0; column < matrix[row].length; column++) {
        matrix[row][column] = input.nextDouble();
      }
    }
    sumColumn(matrix,0);
  }
  public static double sumColumn(double[][] m, int columnIndex) {
        double total = 0;
        for (int column = 0; column <= columnIndex; column++) {
          total = 0;
          for (int row = 0; row < m.length; row++) {
            total += m[row][column];
           //System.out.println("The sum for column "+column+" until row "+row+" is " + total);
          }              
         System.out.println("The sum for column "+ column + " is " + total);            

        }
        return total;
}
}

推荐答案

在大多数情况下，该程序对我而言都是正确的.以下是一些小调整:

The program looks correct to me for most parts. Here are some minor tweaks:

import java.util.Scanner;

public class SumColumnElements {

  public static final int ROW = 3;
  public static final int COLMN = 4;

  public static void main(String[] args) {
    double[][] matrix = new double [ROW][COLMN];

    Scanner input = new Scanner(System.in);
    System.out.println("Enter " + matrix.length + " rows and " + matrix[0].length + " columns:");
    for (int row = 0;row < matrix.length; row++) {
      for (int column = 0; column < matrix[row].length; column++) {
        matrix[row][column] = input.nextDouble();
      }
    }
    sumColumn(matrix, COLMN);
  }
  public static double sumColumn(double[][] m, int columnIndex) {
    System.out.println("columnIndex: " + columnIndex);
    double total = 0;
    for (int column = 0; column < columnIndex; column++) {
      total = 0;
      for (int row = 0; row < m.length; row++) {
        total += m[row][column];
      }
      System.out.println("The sum for column "+ column + " is " + total);
    }
    return total;
  }
}

对于特定输入:

1  2  3  4

5  6  7  8

9 10 11 12

输出将是:

The sum for column 0 is 15.0
The sum for column 1 is 18.0
The sum for column 2 is 21.0
The sum for column 3 is 24.0

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