C++ How to generate 10,000 UNIQUE random integers to store in a BST?

I am trying to generate 10,000 unique random integers in the range of 1 to 20,000 to store in a BST, but not sure the best way to do this.

I saw some good suggestions on how to do it with an array or a vector, but not for a BST. I have a contains method but I don't believe it will work in this scenario as it is used to search and return results on how many tries it took to find the desired number. Below is the closest I've gotten but it doesn't like my == operator. Would it be better to use an array and just store the array in the BST? Or is there a better way to use the below code so that while it's generating the numbers it's just storing them right in the tree?

for (int i = 0; i < 10000; i++) 
{
    int random = rand() % 20000;
    tree1Ptr->add(random);
    for (int j = 0; j < i; j++) {
        if (tree1Ptr[j]==random) i--;
        }
    }