CODEWITHSUNDEEP
carrayspointersstructpermutation
Abeer
Abeer

Reputation: 69

Matrix of permutations?

so i have a matrix struct and i have to fill with permutations ranging from 0~nr_vals in N columns. I finished the permutation part but i cannot figure out the pointers with the array. Any Help would be appreciated. There is a printing function that i call and all i does it prints and thats it. Its supposed to print the permutations(DONE) after allocating them to the matrix. what am i doing wrong and also how do i free the matrix?

printing function:

void print_2D(matrix_ptr mat);

struct matrix_2D_struct {
    int** data_arr;
    int rows;
    int cols;
};
typedef struct matrix_2D_struct * matrix_ptr;

matrix_ptr perm_rec_2(int N, int nr_vals) {
    struct matrix_2D_struct *matrix = malloc(sizeof *matrix);
    int j = 0;
    int i = 0;
    prem_rec_helpTwoForMatrix (N, nr_vals, i, matrix->data_arr, j);
    return NULL;
}

void prem_rec_helpTwoForMatrix(int N, int nr_vals, int i, int **a[], int j)
{
    i = N - 1;
    while(a[i][j] < nr_vals){
        a[i][j]++;
    }
    while(i >= 0 && a[i][j] == nr_vals){
        i--;
    }
    if(i < 0)
    {
        return;
    }
    a[i][j]++;
    while(++i < N)
    {
        a[i] = 0;
    }
    prem_rec_helpTwoForMatrix(N, nr_vals, i, **a, j);
}

Upvotes: 1

Views: 78

Answers (1)

Barmak Shemirani
Barmak Shemirani

Reputation: 31669

This is a partial answer:

After allocating matrix, you have to allocate matrix->data_arr.

Assuming that the array is NxN large:

struct matrix_2D_struct *matrix = malloc(sizeof *matrix);

if (N < 1)
{
    printf("error!\n");
    return ...
}

matrix->data_arr = malloc(N*sizeof(int*));
int i, j;
for (i = 0; i < N; i++)
    matrix->data_arr[i] = malloc(N*sizeof(int));

Initialization (as suggested in comment)

for (i = 0; i < N; i++)
    for (j = 0; j < N; j++)
        matrix->data_arr[i][j] = 0;

Now you can test to see if it works:

matrix->data_arr[2][0] = 20;
matrix->data_arr[0][4] = 4;
printf("%d\n", matrix->data_arr[2][0]);
printf("%d\n", matrix->data_arr[0][4]);

When you no longer need the data, you can free it (the data is freed automatically when you exit the program)

for (i = 0; i < N; i++)
    free(matrix->data_arr[i]);
free(matrix->data_arr);
free(matrix);

Upvotes: 1

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