"Sword means offer" Q40: the number of occurrences in an array

There is some trouble with the inference of classification in the book, which is to classify an array of elements by one for 0. If the 3rd digit is 1. So the element x & 8 equals or is not equal to 0, so it is not necessary to infer with the first few.

def once (array): Reor = 0for x in array:reor ^= xbit1 = firstBit1 (reor) first = 0second = 0for x in array:if x & bit1! = 0:first ^= Xelse:second ^= xreturn First, Seconddef firstBit1 (x): n = 1while true:if x & n! = 0:return nelse:n << ; = 1

"Sword means offer" Q40: the number of occurrences in an array