Find 2 missing numbers in an array of integers with two missing values

Question

How do you do this? The values are unsorted but are of [1..n] Example array [3,1,2,5,7,8]. Answer: 4, 6

I saw this solution in

Answer 1

I hope this program is useful to you all, i took the limit till 10 it can be done the same way, just use n as the limit and perform the same operations.

#include 
#include

using namespace std;

int main()
{
    int i,x[100],sum1=0,sum2=0,prod1=1,prod2=1,k,j,p=0;
    cout<<"Enter 8 elements less than 10, they should be non recurring"<>x[i];
    }
    sum1=((10)*(11))/2;
    for(i=0;i<8;i++)
    {
        sum2+=x[i];
    }
    k=sum1-sum2;
    for(i=1;i<10;i++)
    {
        prod1=prod1*i;
    }
    for(i=0;i<8;i++)
    {
        prod2=prod2*x[i];
    }
    j=prod1/prod2;
    p=sqrt((k*k)-(4*j));
    cout<<"One missing no:"<