如何在C中创建一个2D数组并使用指针和函数显示

Question

我正在尝试编写2个函数，一个函数读取矩阵（2D数组），另一个读取矩阵（2D数组）。到目前为止，我有：

    /* Read a matrix: allocate space, read elements, return pointer. The
       number of rows and columns are given by the two arguments. */
    double **read_matrix(int rows, int cols){
        double **mat = (double **) malloc(sizeof(double *)*rows);
        int i=0;
        for(i=0; i<rows; i++){
        /* Allocate array, store pointer  */
        mat[i] = (double *) malloc(sizeof(double)*cols); 
       //what to do after??
         return mat;
    }

然后打印矩阵函数，不确定它是否正确

void print_matrix(int rows, int cols, double **mat){
    for(i=0; i<rows; i++){    /* Iterate of each row */
      for(j=0; j<cols; j++){  /* In each row, go over each col element  */
      printf("%f ",mat[i][j]); /* Print each row element */
  }
}
}

这是我用来运行的主要功能：

    #include <stdlib.h>

    double **read_matrix(int rows, int cols);
    void print_matrix(int rows, int cols, double **mat);
    void free_matrix(int rows, double **mat);
    int main(){
      double **matrix;
      int rows, cols;
      /* First matrix */
      printf("Matrix 1n");
      printf("Enter # of rows and cols: ");
      scanf("%d %d",&rows,&cols);
      printf("Matrix, enter %d reals: ",rows*cols);
      matrix = read_matrix(rows,cols); 
      printf("Your Matrixn");  /* Print the entered data */
      print_matrix(rows,cols,matrix);
      free_matrix(rows, matrix);   /* Free the matrix */
        return 0;
}

Answer 1

尝试这个。可能对您有帮助。

#include <stdio.h>
#include <stdlib.h>
double **read_matrix(int rows, int cols);
void print_matrix(int rows, int cols, double **mat);
void free_matrix(int rows, double **mat);
double **read_matrix(int rows, int cols){
    double **mat = (double **) malloc(sizeof(double *)*rows);
    int i=0,j=0;
    for(i=0; i<rows; i++)
    /* Allocate array, store pointer  */
        mat[i] = (double *) malloc(sizeof(double)*cols); 
       for(i=0; i<rows; i++){
           for(j=0; j<cols; j++){
               scanf("%lf",&mat[i][j]);
           }
       }
     return mat;
}
void print_matrix(int rows, int cols, double **mat){
    int i=0,j=0;
  for(i=0; i<rows; i++){    /* Iterate of each row */
        for(j=0; j<cols; j++){  /* In each row, go over each col element  */
            printf("%lf ",mat[i][j]); /* Print each row element */
        }
        printf("n");
    }
}
void free_matrix(int rows, double **mat){
    int i=0;
    for(i=0;i<rows;i++)    
        free(mat[i]);
    free(mat);
}
int main(){
  double **matrix;
  int rows, cols;
  /* First matrix */
  printf("Matrix 1n");
  printf("Enter # of rows and cols: ");
  scanf("%d%d",&rows,&cols);
  printf("Matrix, enter %d reals: n",rows*cols);
  matrix = read_matrix(rows,cols); 
  printf("Your Matrixn");  /* Print the entered data */
  print_matrix(rows,cols,matrix);
  free_matrix(rows, matrix);   /* Free the matrix */
  return 0;
 }

执行：

:~$ gcc  exam.c
:~$ ./a.out 
Matrix 1
Enter # of rows and cols: 3
4
Matrix, enter 12 reals: 
1
2
3
4
5
6
7
8
9
9
0
1
Your Matrix
1.000000 2.000000 3.000000 4.000000 
5.000000 6.000000 7.000000 8.000000 
9.000000 9.000000 0.000000 1.000000