The true insight here is not using XOR, it's sliding the window efficiently. Here is pseudocode not using XOR. members = [0]*len(alphabet) for i in 0.

The true insight here is not using XOR, it's sliding the window efficiently. Here is pseudocode not using XOR. members = [0]*len(alphabet) for i in 0...input length: members[input[i-window_size]] = 0 if bounds ok members[input[i]] = 1 if sum(members) == window_size: return i If `members` is a bit vector and `sum()` is a popcount, this code is equivalent.