Generate Distinct random numbers

Question

I'm trying to generate 100 distinct random numbers between 0 to 800 and repeat the random number generation 10 times then separate the numbers using a comma but i'm having a problem. In this example i'm using a 2D array to achieve this but I don't seem to get it working.

int main(void)
{
  int table[10][10];
  int i;
  int nSize = sizeof(table)/sizeof(int);

  for (i = 0; i < nSize; i++)
  {
     for (j = 0; j < nSize; j++)
        printf("%d,",table[i][j] = rand() % 800);
  }
  printf("\n");
}

The output is supposed to look something similar to the following:

1, 3, 500, 400, 322, ...
2, 5, 200, 321, 212, ...
500, 433, 421, 354, 545, ...
..
..
..
..
..
..
500, 321, 314, 434, 343, ...

The above is an example and not the actual values.

Answer 1

1. One of the dimensions of table should be 100, since you have 100 random numbers.
2. In the inner loop, you should either make sure the random number has not already been generated, or (more complex and more efficient) use some kind of shuffling algorithm.
3. Does rand() % 800 produce a number between 0 and 800?

Answer 2

#define ROW 10
#define COL 10
int array[ROW][COL];
for (i = 0; i < ROW; i++) {
    for (j = 0; j < COL; j++) {
        array[i][j] = rand() % 801; // if rand() % 800, then it generate 0 - 799, never 800

Answer 3

Just move the printf("\\n") into the outer for loop and you don't have to use an array:

int main(void)
{
    for (int i = 0; i < 10; i++) {
        for (int j = 0; j < 10; j++) {
            printf("%s%d", j > 0 ? "," : "", rand() % 800);
        }
        printf("\n");
    }
}

Note: this will generate numbers between 0 and 799.