使用扫描仪将元素插入二维数组时出现逻辑错误

Question

>我正在尝试矩阵的行数之和 当我只是将元素放入 2D 数组输出是正确的，但是当我尝试使用扫描仪输出结果时是不同的

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，而应该只读取行数和列数的单个整数：

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，保持代码干净和用户友好同样重要。如果你认真对待编程，我建议你解决以下几点：

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. 您无需为此代码声明带有mainthrows IOException。

4. 您应该始终显示一条描述输入的消息;否则，用户仍然不知道他/她应该输入什么。

   下面给出的是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);
   }
   }
   }
   

   运行示例：

   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