Repeating Array elements - c++

Question

I am running a code for finding repeating array elements.
I am doing it using 2 functions, however when I run the code my application immedietaly crashes despite assigning it to random numbers from 1 to 99.
Here is the code. Thank you..
#include <ctime>
#include <iostream>
using namespace std;
int UniqueArray(int arr[], int notunique);
void printarray(int arr[]);
int main() {
int arr[20];
int dup = 0;
printarray(arr);
for (int i = 0; i < 20; ++i) {
UniqueArray(arr, dup);
}
}
int UniqueArray(int arr[], int notunique) {
notunique = 0;
int i, j;
int size = sizeof(arr) / sizeof(arr[0]);
for (i = 0; i < size; i++) {
for (j = i + 1; j < size; j++) {
if (arr[i] == arr[j]) {
notunique++;
cout << "Array has duplicates: " << arr[i] << " ";
}
}
}
return notunique;
cout << "There were " << notunique << " Repeated elements";
}
void printarray(int arr[]) {
int size = sizeof(arr) / sizeof(arr[0]);
srand(time(0));
arr[20] = rand () % +100;
for (int i = 0; i < 20; ++i) {
cout << arr[i] << " ";
}
}

Answer 1

This line:
arr[20] = rand () % +100;
does not fill an array of size 10 with random values. It indexes the 20th position, which is UB.
You could fill the array with random numbers, using std::generate, like this:
std::generate(arr, arr + 20, [] { return rand() % 100; });
Also, when finding the size of the array, you'll need to deduce the size:
template <size_t N>
void printarray(int (&arr)[N]) {
// ... use N which is the size of arr
or even better, use std::array, which does this for you.
Some minor issues:
Don't use using namespace std;.
In this snippet:
return notunique;
cout << "There were " << notunique << " Repeated elements";
the statement after the return will never get executed.
In this line:
arr[20] = rand () % +100;
you don't need the + operator.