Two Numbers Without a Partner

In the list nums, every value appears exactly twice, except two different values that appear once each. Write find_two(nums) that returns those two values as a list, smaller first.

The real goal is to do it with a fixed, small amount of extra memory however long the list is: no dictionary, set or counter that grows with the list, and no sorting a copy. The tests can only check the answer, but this is the skill the problem is here to teach.

Examples

find_two([4, 1, 2, 1, 2, 7])  # returns [4, 7]
find_two([10, -3])            # returns [-3, 10]
find_two([5, 9, 5, 0, 9, 8])  # returns [0, 8]

Constraints

• 2 <= len(nums) <= 200,000
• -10**9 <= nums[i] <= 10**9