Passing a matrix in a function (C)

问题

I have an issue passing a matrix to a function in C. There is the function I want to create:

void ins (int *matrix, int row, int column);

but I noticed that in contrast to the vectors, matrix give me an error. How can I pass my matrix to a function so?

EDIT --> there is the code:

// Matrix

#include <stdio.h>
#define SIZE 100

void ins (int *matrix, int row, int column);
void print (int *matrix, int row, int column);

int main ()
{
    int mat[SIZE][SIZE];
    int row, col;

    printf("Input rows: ");
    scanf  ("%d", &row);
    printf("Input columns: ");
    scanf  ("%d", &col);

    printf ("Input data: \n");
    ins(mat, row, col);

    printf ("You entered: ");
    print(mat, row, col);

    return 0;
}

void ins (int *matrix, int row, int column);
{
    int i, j;

    for (i = 0; i < row; i++)
    {
        for (j = 0; j < column; j++)
        {
            printf ("Row %d column %d: ", i+1, j+1);
            scanf  ("%d", &matrix[i][j]);
        }
    }
}

void print (int *matrix, int row, int column)
{
    int i;
    int j;

    for(i=0; i<row; i++)
    {
        for(j=0; j<column; j++)
        {
            printf("%d ", matrix[i][j]);
        }
        printf("\n");
    }
}

回答1:

You must pass the number of dimensions as pointers,

i.e. if your matrix is 2D (10 by 100), then:

void ins (int **matrix, int row, int column);

but the previous is wrong, since any static 2D array requires that second level of pointers be constpointer to static array. The previous header would be correct if the matrix is dynamic array. so the correct is:

void ins (int (*matrix)[100], int row, int column);

or in your case:

void ins (int (*matrix)[SIZE], int row, int column);

or simply:

void ins (int matrix[10][100], int row, int column);

or in your case:

void ins (int matrix[SIZE][SIZE], int row, int column);

回答2:

If you have a modern C compiler you can do the following for 2D matrices of any sizes

void ins (size_t rows, size_t columns, int matrix[rows][columns]);

Important is that the sizes come before the matrix, such that they are known, there.

Inside your function you then can access the elements easily as matrix[i][j] and the compiler is doing all the index calculations for you.

回答3:

it would also possible to leave the first dimension empty, the same as (*matrix):

void ins (int matrix[][100], int row, int column);

回答4:

C - allocating a matrix in a function

Above you will find a program that I have made with functions allocating and manipulating matrices in any possible way for C (gcc C11/C99).

回答5:

Much better way to use malloc function and create dynamically allocated array and do whatever you want to do using 2d array:

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

void fun(int **arr,int m,int n)
{
    int i, j;
    for (i = 0; i < m; i++)
    {
    for (j = 0; j < n; j++)
        {
            scanf("%d", &arr[i][j]);
        }
    }

}

int main()
{
    int i,j,m,n;
    printf("enter order of matrix(m*n)");
    scanf("%d*%d",&m,&n);
    int **a=(int **)malloc(m*sizeof(int));
    for(i=0;i<n;i++)
        a[i]=(int *)malloc(n*sizeof(int));

    fun(a,m,n);
    for (i = 0; i < m; i++)
    {
    for (j = 0; j < n; j++)
        {
        printf("%d ", a[i][j]);
        }
        printf("\n");

    }
    return 0;
}

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

void fun(int **arr,int m,int n)
{
    int i, j;
    for (i = 0; i < m; i++)
    {
    for (j = 0; j < n; j++)
        {
            scanf("%d", &arr[i][j]);
        }
    }

}

int main()
{
    int i,j,m,n;
    printf("enter order of matrix(m*n)");
    scanf("%d*%d",&m,&n);
    int **a=(int **)malloc(m*sizeof(int));
    for(i=0;i<n;i++)
        a[i]=(int *)malloc(n*sizeof(int));

    fun(a,m,n);
    for (i = 0; i < m; i++)
    {
    for (j = 0; j < n; j++)
        {
        printf("%d ", a[i][j]);
        }
        printf("\n");

    }
    return 0;
}

来源：https://stackoverflow.com/questions/11428526/passing-a-matrix-in-a-function-c

标签

matrix