使用扫描仪将元素插入二维数组时出现逻辑错误

Question

我正在尝试对矩阵行求和当我只是将元素放入二维数组 output 是正确的但是当我尝试使用扫描仪 output 结果是不同的

样本输入

2
1 2 
3 4

Output：

3
7

下面的代码结果正确

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 。

   您应该删除所有在您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. 对于此代码，您不需要使用main声明throws IOException 。

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

   下面给出了包含这些注释的代码：

    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