c - 读取未知维度的矩阵

Question

这个问题已经有答案了:

reading matrices from a file and retriving their dimension (2 个回答)

已关闭 4 年前。

我正在尝试从以此方式格式化的文件中读取矩阵

1 2 3 44 5 6 78 9 10 11*1 0 10 1 11 1 1]

but I don't know how to pass the multidimensional array with its dimension given by rows[] and cols[] arrays to the function read_matrix().

I am able to get the correct dimension of the two matrices

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

int get_dim(char *file, int *r, int *col);
/*gets the dimension and type of operation*/

void read_matrix(char *file, int (*matA)[], int(*matB)[], int *m, int *n);

int main (int argc, char *argv[]){

    int i,j;
    int rows[2]= {0,1}; /* The last line of the file does not contain '\n' */
    int cols[2]= {0,0};
    int operation; /*type of operation 1 for * and 2 for + */

    operation = get_dim(argv[1], rows, cols);

    int A[rows[0]][cols[0]];
    int B[rows[1]][cols[1]];

    printf("A is a matrix %d x %d\n",rows[0], cols[0]);

    if(operation != 0)
        printf("B is a matrix %d x %d\n", rows[1], cols[1]);

    read_matrix(argv[1], A, B, rows, cols);

    /*printing the matrices */

    for(i = 0; i < rows[0]; i++){
        for(j=0; j < cols[0]; j++){
            printf("%d ", A[i][j]);
        }
        printf("\n");
    }

    printf("*\n");

     for(i = 0; i < rows[1]; i++){
        for(j=0; j< cols[1]; j++){
            printf("%2d ", B[i][j]);
        }
        printf("\n");
    }    
    return 0;
}

int get_dim(char *file, int *r, int *col){

   FILE *fp; 
   int c;
   int op=0;
   int n =0; /*to check all coefficients in a row */

   /* opening file for reading */
   fp = fopen(file, "r");

   if(fp == NULL) {
      perror("Error opening file");
   }

   while ( (c = getc(fp)) != ']')
   {       
       if(isdigit(c) && n==0){
           if(op == 0)
               col[0]++;
           else
               col[1]++;
       }        

    //Count whenever new line is encountered
    if (c == '\n'){
        n=1;
        if(op == 0)
            r[0]++;
        else 
            r[1]++;
    }     

        if(c == '*'){
            op=1;
            n =0;
            c = getc(fp);
        }
        else if(c == '+'){
            op=2;
            c = getc(fp);
        }

        //take next character from file.
    }
    fclose(fp);
    return op;
}

void read_matrix(char *file, int (*matA)[], int(*matB)[], int *m, int *n){

    int i,j;
    FILE *fp;

    if( (fp = fopen(file, "r")) != NULL ){

        for(i=0; i < m[0]; i++)
            for(j=0; j < n[0]; j++)
                fscanf(fp, "%d", &matA[i][j]);    

        /*skip the line containing the character operator */
        while ( fgetc(fp) != '\n')
            fgetc(fp);        

        for(i=0; i < m[1]; i++)
            for(j=0; j < n[1]; j++)
                fscanf(fp, "%d", &matB[i][j]);    
    }

    fclose(fp);
}

我应该这样定义指针:int(*matA)[cols[0]] 和 int(*matB)[cols[1]]。在 read_matrix() 中，通过声明此指针: int(*matB)[] 我收到错误:无效使用具有未指定边界的数组，据我所知。但界限是由 get_dim() 函数确定的。

Answer 1

get_dim 函数的结果在运行时确定，而像 matA 这样的静态数组的大小必须在编译时确定。例如，采用以下代码:

volatile size_t length = 5;
int myArray[length];

或者另一个例子:

size_t length;
//take input from the user...
int myArray[length]

这些示例无法编译，因为长度只能在运行时确定。

您必须使用动态分配的数组来完成您想做的事情。