Question

我试图从两个文本文件中读取矩阵，将其存储到2个数组中，然后尝试将两个矩阵相乘并将结果存储在数组中。乘法结果为000。

以下是我的代码

#include<stdio.h>
#include<stdlib.h>

int main(int argc,char *argv[])
{
    FILE *fr1, *fr2, *fw;
    char *line = malloc(1000);
    int count = 0;
    //To read a file use the fopen() function to open it 
    fr1 = fopen(argv[1], "r");
    //If the file fails to open the fopen() returns a NULL 
    if (fr1 == NULL) {
        printf("Cannot open %s. Program terminated...",argv[1]);
        exit(1);
    }

    // Similar to the above method read the second file
    fr2 = fopen(argv[2], "r");
    if (fr2 == NULL) {
        printf("Cannot open %s. Program terminated...",argv[2]);
        exit(1);
    }

    double *data = (double*) malloc(1000*sizeof(double));
    if(data == NULL)
    {
        printf("Error in allocating memory");
        return EXIT_FAILURE;
    }
    // Read number of columns and number of rows of first matrix
    getline(&line, &count, fr1);
    int read = -1, cur = 0, columCount1 = 0;
    while(sscanf(line+cur, "%lf%n", &data[columCount1], &read) == 1)
    {cur+=read; columCount1++;}

    int rowCount1 = 1;
    while(getline(&line, &count, fr1) != -1) {rowCount1++;}
    printf("%d\n",columCount1);
    printf("%d\n",rowCount1);

    // Read number of columns and number of rows of second matrix
    getline(&line, &count, fr2);
    read = -1,cur = 0;
    int columCount2 = 0;
    while(sscanf(line+cur, "%lf%n", &data[columCount2], &read) == 1)
    {cur+=read; columCount2++;}

    int rowCount2 = 1;
    while(getline(&line, &count, fr2) != -1) {rowCount2++;}
    printf("%d\n",columCount2);
    printf("%d\n",rowCount2);
    int i=0;
    int j=0;

    int **mat1 = (int **)malloc(rowCount1 * sizeof(int*));
    for(i = 0; i < rowCount1; i++)
    mat1[i] = (int *)malloc(columCount1 * sizeof(int));

    fseek( fr1, 0, SEEK_SET );

    for(i=0; i<rowCount1; i++)
    {
        for(j=0; j<columCount1; j++)
            fscanf(fr1,"%d",&mat1[i][j]);
    }

    i = 0;
    j = 0;

    printf("\n\n");
    //print matrix 1
    for(i=0; i<rowCount1; i++)
    {
        for(j=0; j<columCount1; j++)
            printf("%d",mat1[i][j]);

        printf("\n");
    }

    i = 0;
    j = 0;
    int **mat2 = (int **)malloc(rowCount2 * sizeof(int*));
    for(i = 0; i < rowCount2; i++)
        mat2[i] = (int *)malloc(columCount2 * sizeof(int));

    fseek( fr2, 0, SEEK_SET );

    for(i=0; i<rowCount2; i++)
    {
        for(j=0; j<columCount2; j++)
            fscanf(fr2,"%d",&mat2[i][j]);
    }

    i = 0;
    j = 0;

    printf("\n\n");
    //print matrix 2
    for(i=0; i<rowCount2; i++)
    {
        for(j=0; j<columCount2; j++)
            printf("%d",mat2[i][j]);

        printf("\n");
    }

    i = 0;

    int **mat3 = (int **)malloc(rowCount1 * sizeof(int*));
    for(i = 0; i < rowCount1; i++)
        mat3[i] = (int *)malloc(columCount2 * sizeof(int));
    i = 0;
    j = 0;
    int k = 0;
    int sum = 0;
    //multiplication of two matrices
    for(i=0; i<rowCount1; i++)
    {
        for(j=0; j<columCount2; j++)
        {
            sum=0;
            for(k=0; k<rowCount2; k++)
                sum+=mat1[i][k]*mat2[k][j];
        }
        mat3[i][j] = sum;
    }

    i = 0;
    j = 0;


    //print multiplication result
    printf("\n\nResult = \n\n");

    for(i=0; i<rowCount1; i++)
    {
        for(j=0; j<columCount2; j++)
            printf("%d",mat3[i][j]);

        printf("\n");
    }

    return 0;   
}

Answer 1

1）在矩阵乘法之前检查矩阵1中的列数是否与矩阵2中的行数相同

//Check if number of col in mat1 is same as number of rows in mat2
if(columCount1 != rowCount2)
{
    puts("The number of columns in Matrix 1 is not same as the number of rows in Matrix 2");
    exit(1);
}

2）两个矩阵相乘的代码：

for(i=0;i<rowCount1;i++)
{
    for(j=0;j<columCount2;j++)
    {
        mat3[i][j]=0;
        for(k=0;k<columCount1;k++)
        {
            mat3[i][j] = mat3[i][j]+mat1[i][k] * mat2[k][j];
        }
    }
}

3）从main()

返回之前释放分配的内存

/* After printing the results free the memory */
for(i=0; i< rowCount1; i++)
    free( mat1[i]);
free(mat1);

for(i=0; i< rowCount2; i++)
    free( mat2[i]);
free(mat2);

for(i=0; i< rowCount1; i++)
    free( mat3[i]);
free(mat3);

free(data);

将两个矩阵与两个文本文件相乘得出输出为零

1 个答案: