使用扫描仪将元素插入二维数组时出现逻辑错误

Question

我正在尝试对矩阵的行求和 当我将元素放入二维数组时输出是正确的，但是当我尝试使用扫描仪时输出结果不同

示例输入

2
1 2 
3 4

输出：

3
7

以下代码结果正确

import java.io.*;
import java.util.*;

public class matrix {
    public static void main(String[] args) throws IOException {
       Scanner sc = new Scanner(System.in);

 int a[][] = {       
                        {1, 2,},    
                           
                        { 3, 4}    
                    };    

int rows, cols, sumRow, sumCol;    
            
        //Initialize matrix a  
              
          //Calculates number of rows and columns present in given matrix    
          rows = a.length;    
        cols = a[0].length;    
            
        //Calculates sum of each row of given matrix    
        for(int i = 0; i < rows; i++){    
            sumRow = 0;    
            for(int j = 0; j < cols; j++){    
              sumRow = sumRow + a[i][j];    
            }    
            System.out.println(sumRow);    
        }    
            
        //Calculates sum of each column of given matrix    
        for(int i = 0; i < cols; i++){    
            sumCol = 0;    
            for(int j = 0; j < rows; j++){    
              sumCol = sumCol + a[j][i];    
            }
        }
    }
}

如果我尝试使用扫描仪，结果不正确

import java.io.*;
import java.util.*;

public class matrix {
    public static void main(String[] args) throws IOException {
       Scanner sc = new Scanner(System.in);

int row = sc.nextInt();

int column = sc.nextInt();

int [][] a = new int[row][column];
for (int i = 0; i < row; i++)
{
    for(int j = 0; j < column; j++) {
       
    a[i][j] = sc.nextInt(); 
    }
}

int rows, cols, sumRow, sumCol;    
            
        //Initialize matrix a  
              
          //Calculates number of rows and columns present in given matrix    
          rows = a.length;    
        cols = a[0].length;    
            
        //Calculates sum of each row of given matrix    
        for(int i = 0; i < rows; i++){    
            sumRow = 0;    
            for(int j = 0; j < cols; j++){    
              sumRow = sumRow + a[i][j];    
            }    
            System.out.println(sumRow);    
        }    
            
        //Calculates sum of each column of given matrix    
        for(int i = 0; i < cols; i++){    
            sumCol = 0;    
            for(int j = 0; j < rows; j++){    
              sumCol = sumCol + a[j][i];    
            }           
        }
    }
} 

Answer 1

使用您提供的示例输入，您不应该读取行数和列数，而只是读取行数和列数的单个 int：

int size = sc.nextInt();

int [][] a = new int[size][size];
for (int i = 0; i < size; i++) {
    for(int j = 0; j < size; j++) {       
        a[i][j] = sc.nextInt(); 
    }
}

Answer 2

我认为您的代码没有任何逻辑问题。但是，保持代码整洁和用户友好同样重要。如果您对编程很认真，我建议您解决以下几点：

1. 以下声明是不必要的：

   rows = a.length;
   cols = a[0].length;
   

   您可以简单地使用row 和column，而不是为同一事物创建rows 和cols。

   你应该删除所有在你的代码中产生噪音的不必要的东西。

2. 您错过了打印每列的总和，即

   System.out.println(sumCol);
   

3. 您不需要为此代码声明throws IOException 和main。

4. 您应该始终显示一条描述输入的消息；否则，用户对他/她应该输入什么一无所知。

   下面是包含这些 cmets 的代码：

   import java.util.Scanner;
   
   public class Main {
       public static void main(String[] args) {
           Scanner sc = new Scanner(System.in);
   
           System.out.print("Enter the number of rows: ");
           int row = sc.nextInt();
           System.out.print("Enter the number of columns: ");
           int column = sc.nextInt();
   
           int[][] a = new int[row][column];
           for (int i = 0; i < row; i++) {
               System.out.println("Enter " + column + " integers: ");
               for (int j = 0; j < column; j++) {
                   a[i][j] = sc.nextInt();
               }
           }
   
           int sumRow, sumCol;
   
           // Calculates sum of each row of given matrix
           for (int i = 0; i < row; i++) {
               sumRow = 0;
               for (int j = 0; j < column; j++) {
                   sumRow = sumRow + a[i][j];
               }
               System.out.println("Sum of row " + i + ": " + sumRow);
           }
   
           // Calculates sum of each column of given matrix
           for (int i = 0; i < column; i++) {
               sumCol = 0;
               for (int j = 0; j < row; j++) {
                   sumCol = sumCol + a[j][i];
               }
               System.out.println("Sum of column " + i + ": " + sumCol);
           }
       }
   }
   

   示例运行：

   Enter the number of rows: 3
   Enter the number of columns: 4
   Enter 4 integers: 
   1 9 2 8
   Enter 4 integers: 
   2 8 3 7
   Enter 4 integers: 
   3 7 4 6
   Sum of row 0: 20
   Sum of row 1: 20
   Sum of row 2: 20
   Sum of column 0: 6
   Sum of column 1: 24
   Sum of column 2: 9
   Sum of column 3: 21