C++ สร้าง array ขนาด 20 ช่อง มีกี่จำนวนที่ซ้ำกัน และจำนวนอะไรบ้างที่ซ้ำกัน

#define max 20
int a[max];
int b[max];
int count = 0;
//bubble sort
srand(time(NULL));
for (int i = 0; i < max; i++)
{
cout << "Enter a[" << i + 1 << "] : ";
cin >> a[i];
}
for (int i = 0; i < max; i++)
{
if (i % 4 == 0)
cout << endl<<endl;
cout << a[i] << "\t";
}
for (int j = 0; j < max; j++)
{
for (int i = 0; i < max - 1; i++)
{
if (a[i] > a[i + 1])
{
int temp;
temp = a[i];
a[i] = a[i + 1];
a[i + 1] = temp;
}
}
}
for (int i = 0; i < max; i++)
{
if (a[i] < 999)
{
b[i] = 1;
for (int j = i + 1; j < max; j++)
{
if (a[i] < 999)
{
if (a[i] == a[j])
{
b[i] = b[i] + 1;
a[j] = 999;
}
}
}
}
}
cout <<endl<< "--------------------------";
cout << endl<<endl;
for (int i = 0; i < max; i++)
{
if (a[i] < 999 && b[i] != 1)
count++;
}
cout << count << endl;
cout << endl;
for (int i = 0; i < max; i++)
{
if (a[i] < 999 && b[i] != 1)
cout << a[i] << " = " << b[i] << endl;
}