This time the array hides not one lone value but two — every other number is matched with a twin, while these two odd ones out have no partner anywhere in the array. Track both down and hand them back, in whichever order is convenient. A single XOR pass over the whole array cancels every paired value, but with two different singles left over instead of one, the result is a ^ b rather than a clean answer on its own. The fix is to find one bit where a and b must disagree (any bit set in a ^ b works), and use it to split every number into two groups — XOR-ing each group separately then isolates one single per group.