使用数组乘以矩形矩阵的 C 程序不打印结果矩阵

Question

我努力编写了一个用于矩形矩阵乘法的C程序，但是当编译并运行该程序时，结果矩阵没有随乘积一起打印。作为用户输入，我尝试为矩阵 A 输入 2 行和 3 列，为矩阵 B 输入 3 行和 2 列。

如何更正以下代码？

#include<stdio.h>
int main()
{
    int i,j,r,c,r1,c1,r2,c2,k,a[10][10],b[10][10],result[10][10];
    printf("\n Enter the no. of rows and column desired for the 1st matrix (between 1 to 10):");
    scanf("%d%d",&r1,&c1);
    printf("\n Enter the no. of rows and columns for the 2nd matrix - between 1 to 10 (Pls note that no. of rows of 1st matrix should be equal to the no. of columns in the 2nd matrix for multiplication):");
    scanf("%d%d",&r2,&c2);
    
    printf("\n Enter the elements of the 1st Matrix:");
    for(i=0;i<r1;i++){
        for(j=0;j<c1;j++){
            scanf("%d",&a[i][j]);
        }
    }
    
    printf("\n Print of 1st Matrix:\n");
    for(i=0;i<r1;i++){
        for(j=0;j<c1;j++){
            printf("\t%d",a[i][j]);
        }
        printf("\n");
    }
    
    printf("\n Enter the elements of the 2nd Matrix:");
    for(i=0;i<r2;i++){
        for(j=0;j<c2;j++){
            scanf("%d",&b[i][j]);
        }
    }
    
    printf("\n Print of 2nd Matrix:\n");
    for(i=0;i<r2;i++){
        for(j=0;j<c2;j++){
            printf("\t%d",b[i][j]);
        }
        printf("\n");
    }
    
    //multiplying 1st and 2nd matrices and storing the results in results[i][j]
    for(i=0;i<r1;i++){
        for(j=0;j<c2;j++){
            for(k=0;k<c1;k++){
                result[i][j] = result[i][j] + (a[i][k] * b[k][j]);
            }
        }
    }
    
    //Printing the results
    printf("\n After Multiplication of two matrices:\n");
    for(i=0;i<r;i++){
        for(j=0;j<c;j++){
            printf("\t%d",result[i][j]);
        }
        printf("\n");
    }
    return 0;
}

Answer 1

您的代码存在一些问题。

结果矩阵类型和初始化

您将结果矩阵定义为整数，但是当您执行乘法时，结果始终是浮点数。你有两个解决方案

1. 保存乘法结果时使用显式转换为 int

2. 将结果矩阵类型更改为 float

此外，您应该初始化结果矩阵以避免意外行为。

我建议你这样改代码

float result[10][10]; //define result matrix

...
...
//multiplying 1st and 2nd matrices and storing the results in results[i][j]
       for(i=0;i<r1;i++){
        for(j=0;j<c2;j++){

            //init i,j element of result matrix

            result[i][j] = 0.0;   //add here the initialisation
            for(k=0;k<c1;k++){
                
                result[i][j] = result[i][j] + (a[i][k] * b[k][j]);
            }
        }
    }

打印输出循环

在您的代码中，您使用了变量

r

和

c

，但没有初始化它们。这是错误输出的主要原因。 按如下方式更改代码：

for(i=0;i<r1;i++){
        for(j=0;j<c2;j++){
            printf("\t%f",result[i][j]);
        }
        printf("\n");
    }

新代码

这里是您的程序的完整代码，其中包含更正和 scanf 语句中的一些改进。

#include<stdio.h>
int main()
{
    int i,j,r,c,r1,c1,r2,c2,k,a[10][10],b[10][10];
    float result[10][10];
    printf("\n Enter the no. of rows and column desired for the 1st matrix (between 1 to 10):");
    scanf("%d %d",&r1,&c1);   //put a space between escape codes in order to avoid conversion issues
    printf("\n Enter the no. of rows and columns for the 2nd matrix - between 1 to 10 (Pls note that no. of rows of 1st matrix should be equal to the no. of columns in the 2nd matrix for multiplication):");
    scanf("%d %d",&r2,&c2);   //put a space between escape codes in order to avoid conversion issues
    
    printf("\n Enter the elements of the 1st Matrix:");
    for(i=0;i<r1;i++){
        for(j=0;j<c1;j++){
            scanf("%d",&a[i][j]);
        }
    }
    
    printf("\n Print of 1st Matrix:\n");
    for(i=0;i<r1;i++){
        for(j=0;j<c1;j++){
            printf("\t%d",a[i][j]);
        }
        printf("\n");
    }
    
    printf("\n Enter the elements of the 2nd Matrix:");
    for(i=0;i<r2;i++){
        for(j=0;j<c2;j++){
            scanf("%d",&b[i][j]);
        }
    }
    

    printf("\n Print of 2nd Matrix:\n");
    for(i=0;i<r2;i++){
        for(j=0;j<c2;j++){
            printf("\t%d",b[i][j]);
        }
        printf("\n");
    }
    
    //multiplying 1st and 2nd matrices and storing the results in results[i][j]
       for(i=0;i<r1;i++){
        for(j=0;j<c2;j++){
            //init i,j element of result matrix
            result[i][j] = 0.0;
            for(k=0;k<c1;k++){
                printf("(%d %d %d) %f - %d - %d\n",i,j,k,result[i][j],a[i][k],b[k][j]);
                result[i][j] = result[i][j] + (a[i][k] * b[k][j]);
            }
        }
    }
    
    //Printing the results
    printf("\n After Multiplication of two matrices:\n");
    for(i=0;i<r1;i++){
        for(j=0;j<c2;j++){
            printf("\t%f",result[i][j]);
        }
        printf("\n");
    }
    return 0;
}