Question

我正在研究java加法，减法和乘法程序。我已经创建并完成了程序，但乘法的输出是错误的，我还想检查矩阵乘法中第一个矩阵的行是否等于秒。

import java.util.*;

class matrix
{

public static void matrix_oper(int A[][],int B[][],int m, int n, int p, int q)
{

    int[][] C = new int[m][n];
    System.out.println("Matrix A: ");
    for(int i=0 ; i < A.length ; i++)
    {
        System.out.println();
        for(int j=0 ; j < A[i].length ; j++)
        {
            System.out.print(A[i][j]+" ");
        }
    }
    System.out.println();
    System.out.println();

    System.out.println("Matrix B: ");
    for(int i=0 ; i < B.length ; i++)
    { 
        System.out.println();
        for(int j=0 ; j < B[i].length ; j++)
        {
            System.out.print(B[i][j]+" ");
        }
    }
    System.out.println();
    System.out.println();

    System.out.println("Addition Of Matrices: ");
    for(int i=0;i<C.length;i++)
    {
        for(int j=0;j<C[i].length;j++)
        {
            C[i][j]=A[i][j]+B[i][j];
            System.out.print(C[i][j]+" ");
        }
        System.out.println();
    }

    System.out.println();
    System.out.println();

    System.out.println("Substraction Of Matrices: ");
    for(int i=0;i<C.length;i++)
    {
        for(int j=0;j<C[i].length;j++)
        {
            C[i][j]=A[i][j]-B[i][j];
            System.out.print(C[i][j]+" ");
        }
    System.out.println();
    }

    System.out.println();
    System.out.println();

    System.out.println("Multiplication Of Matrices: ");
    for(int i=0;i<C.length;i++)
    {
        for(int j=0;j<C[i].length;j++)
        {
            C[i][j]=A[i][j]*B[j][i];
            System.out.print(C[i][j]+" ");
        }
        System.out.println();
    }

}


public static void main(String[] args)
{
    Scanner input = new Scanner(System.in);
    System.out.print("Enter Number of rows: ");
    int m = input.nextInt();

    System.out.print("Enter Number of columns: ");
    int n = input.nextInt();
    int[][] A = new int[m][n];

    System.out.print("Enter Number of rows: ");
    int p = input.nextInt();

    System.out.print("Enter Number of columns: ");
    int q = input.nextInt();
    int[][] B = new int[p][q];

    System.out.println("Enter elements for matrix A : ");
    for(int i=0 ; i < A.length ; i++)
        for(int j=0 ; j < A[i].length ; j++)
        {
            A[i][j] = input.nextInt();
        }

    System.out.println("Enter elements for matrix B : ");
    for (int i=0 ; i < B.length ; i++)
        for (int j=0 ; j < B[i].length ; j++)
        {
            B[i][j] = input.nextInt();
        }

    matrix mx=new matrix();
    mx.matrix_oper(A,B,m,n,p,q);
}
}

输出是：

Enter Number of rows: 2
Enter Number of columns: 2
Enter elements for matrix A :
1
1
1
1
Enter elements for matrix B :
2
2
2
2
Matrix A:

1 1
1 1

Matrix B:

2 2
2 2

Addition Of Matrices:
3 3
3 3


Substraction Of Matrices:
-1 -1
-1 -1


Multiplication Of Matrices:
2 2
2 2

我的矩阵乘法中有什么错误？

Answer 1

试试这个

   for (int i = 0; i < rowsInA; i++) {
       for (int j = 0; j < columnsInB; j++) {
           for (int k = 0; k < columnsInA; k++) {
               C[i][j] = C[i][j] + A[i][k] * B[k][j];
           }
       }
   }

Answer 2

乘法逻辑ID错误：矩阵的乘法是通过添加A的行元素和B的列元素的乘法来完成的。试试这个：

int[][] C = new int[m][q]; //this is important. the q.
for(int i=0;i<C.length;i++)
{
    for(int j=0;j<C[i].length;j++) 
    {
        C[i][j]= 0;

          for(k=0;k<n;k++){     //n is column size of A or row size of B.
            C[i][j] += A[i][k]*B[k][j];  //updated
          }
          System.out.print(C[i][j]+" ");
    }
    System.out.println();
}

java中矩阵乘法的错误

2 个答案: