Question

文件中有两个矩阵，格式如下：

17.053 24 1 8 15
23 5 7 14 16
4 6 13 20 22
10 12 19 21 3
11 18 25 2 9

1 3 1 4
0 5 0 4
2 1 2 4

这些只是两个矩阵，它们始终以空行分隔。它们可以是任何大小和形状。我有以下代码读取两个矩阵，并找出每个矩阵的行数和列数。如何将它们输入定义为mat_A和mat_B的两个矩阵中？

我尝试了fscanf，但只打印了0。如何读取应该保存两个二维数组的值？

int main(void)
{

    int space_count = 0;
    int i = 0;
    int j = 0;;
    FILE *fp;
    fp =  fopen("inputformat", "r");
    if(fp == NULL)
        printf("File not read!");
    int NumCols_first, NumCols_second, NumRows_first, NumRows_second;
    int issecondmatrix = 0;
    char *line = NULL;
    size_t len = 0;
    ssize_t read;

    double **mat_A = (double **) malloc(NumRows_first * sizeof(double*));
    for(i=0; i<NumRows_first; i++)
        mat_A[i] = (double *) malloc(NumCols_first * sizeof(double));

    double **mat_B = (double **) malloc(NumRows_second * sizeof(double*));
    for(i=0; i<NumRows_second; i++)
        mat_B[i] = (double *) malloc(NumCols_second * sizeof(double));

    while((read = getline(&line, &len, fp)) != -1){
        printf("Line is of length : %u \n", read);
        printf("Line is:%s\n", line);
        for(i=0; i<read; i++){
            printf("%c\n", line[i]);
            if(line[i] == ' ')
                space_count++;
            if(read == 1){
                printf("Next matrix gonna start after this\n"); 
                NumRows_first = j;
                issecondmatrix = 1;
                j = 0;
            }   
        }
        if(j==1 & issecondmatrix == 0)
            NumCols_first = space_count + 1;
        if(j==1 & issecondmatrix == 1)
            NumCols_second = space_count + 1; 
        space_count = 0;
        j++;
    }
    NumRows_second = j - 1;
    printf("num of columns in first matrix is %d\n", NumCols_first);
    printf("number of rows in first matrix is %d\n", NumRows_first);
    printf("num of columns in second matrix is %d\n", NumCols_second);
    printf("num of rows in second matrix is %d\n", NumRows_second);
    for(i=0; i<NumRows_first)
    {
    for(j=0; j<NumCols_first; j++)
    {
        if(!(fscanf(fp, "%lf", &mat_A[i][j]))
            break;
        printf("%lf", mat_A[i][j]);
    }
}
enter code here




    free(line);
    fclose(fp);
}

Answer 1

示例代码中有几个错误，显而易见的一个错误是在分配内存之前未启动矩阵大小。您可以先扫描文件以找到矩阵的大小并分配内存，然后第二遍扫描以填充矩阵；或者您可以先分配足够大的内存，然后在扫描文件时将其填满。这是一个工作示例，其中忽略了许多错误检查（对于较短的代码）。

#include <stdio.h>
#include <ctype.h>
#include <stdlib.h>
#include <assert.h>
#include <string.h>

int parse_empty(char *word)
{
    for(; *word!='\0'; word++)
        if(!isspace(*word))
            break;
    return (*word=='\0');
}

int parse_line(char *line, float *data, int max)
{
    int n=0; char *p=line, *left=line;
    while((p=strchr(left, ' '))!=NULL) {
        *p='\0';
        if((n<max) && (!parse_empty(left))) {
            data[n] = atof(left);
            n++;
        }
        left = p+1;
    }
    if(!parse_empty(left)) {
        data[n] = atof(left);
        n++;
    }
    return n;
}

#define MAX_LINESZ 128
void parse_matrix(FILE *fp, float *data, int max, int *mm, int *nn)
{
    int m=0, n=0; char *line; size_t len=MAX_LINESZ;
    line = malloc(len*sizeof(char));
    while(getline(&line, &len, fp)!=-1) {
        if(parse_empty(line))
            break;
        n = parse_line(line, data, max);
        data = data+n;
        max  = max-n;
        m++;
    }
    free(line);
    *mm=m; *nn=n;
}

//data must be malloc/calloc memory!
float **matrix_realloc(float *data, int max, int m, int n)
{
    assert(max>=m*n);
    float **mat;
    mat = malloc(m*sizeof(float*));
    mat[0] = realloc(data, m*n*sizeof(float));
    for(int i=1; i<m; i++)
        mat[i] = mat[i-1]+n;
    return mat;
}
void matrix_free(float **matrix)
{
    free(matrix[0]);
    free(matrix);
}

#define MAX_MATRIX (8*8)
int main()
{
    float *data1, *data2;
    int m1, m2, n1, n2;

    FILE *fp = fopen("t.dat", "r");
    data1 = malloc(MAX_MATRIX*sizeof(float));
    data2 = malloc(MAX_MATRIX*sizeof(float));
    parse_matrix(fp, data1, MAX_MATRIX, &m1, &n1);
    parse_matrix(fp, data2, MAX_MATRIX, &m2, &n2);

    float **mat1 = matrix_realloc(data1, MAX_MATRIX, m1, n1);
    float **mat2 = matrix_realloc(data2, MAX_MATRIX, m2, n2);
    for(int i=0; i<m1; i++) {
        printf("1>");
        for(int j=0; j<n1; j++) 
            printf(" %8.2f", mat1[i][j]);
        printf("\n");
    }
    for(int i=0; i<m2; i++) {
        printf("2>");
        for(int j=0; j<n2; j++) 
            printf(" %8.2f", mat2[i][j]);
        printf("\n");
    }
    matrix_free(mat1);
    matrix_free(mat2);
    fclose(fp);
    return 0;
}

从C中的文件读取矩阵

1 个答案: