当我把元素放入2D数组时，我试图求矩阵行的和，输出是正确的，但当我尝试使用扫描仪时，输出结果是不同的
样本输入
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];
}
}
}
}
使用您提供的示例输入，您不应该读取行数和列数，而应该只读取一个用于行数和列数的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();
}
}
我看不出您的代码有任何逻辑问题。 然而，保持代码干净和用户友好同样重要。 如果您对编程很认真，我建议您注意以下几点:
>
以下声明是不必要的:
rows = a.length;
cols = a[0].length;
您可以简单地使用行和列，而不是为同一件事创建行和列。
您应该删除所有这些不必要的东西，这些东西会在代码中产生噪音。
您错过了打印每列的总和，即。
System.out.println(sumCol);
您不需要用main声明此代码的throws IOException。
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。
以下是纳入这些评论的守则:
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
