Puzzle : finding out repeated element in an Array

Question

Size of an array is n.All elements in the array are distinct in the range of [0 , n-1] except two elements.Find out repeated element without using extra temporary array with con

Answer 1

O(n) without the temp array.

a[]={1,0,0,2,3};
i=0;
int required;
while(i= 2 * n)
    required = a[i] % n;
}
print required;

(Assuming of course that n < MAX_INT - 2n)