Algorithm to find two repeated numbers in an array, without sorting

Question

There is an array of size n (numbers are between 0 and n - 3) and only 2 numbers are repeated. Elements are placed randomly in the array.

E.g. in {2, 3, 6, 1, 5, 4

Answer 1

for(i=1;i<=n;i++) {
  if(!(arr[i] ^ arr[i+1]))
        printf("Found Repeated number %5d",arr[i]);
}