C Programming; Producing a 2-Dimensional Matrix with Random Numbers without Repetition

I'd like to produce a 6x6 matrix by inserting random numbers to the elements in the row and column without repeating. This is my code so far. Thank you for your help!

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

int main(void)
{
int array[6][6];
int rows, columns;
int random;

srand((unsigned)time(NULL));

for(rows=0;rows<6;rows++)
    {
        for(columns=0;columns<6;columns++)
            {
                random=rand()%36+1;

                array[rows][columns] = random;
                printf("%i",array[rows][columns]);
            }

        printf("\n");
    }

return 0;
}