There are houses on a straight line. We are given instructions to delete some houses. It is guaranteed that the instructions will be given for valid houses. Return a list of the number of neighboring houses after each instruction.

Example: houses = [2, 1, 3, 4, 6, 7, 9], instructions = [6, 3, 9]. The result should be [3, 4, 3].
Sort the houses: [1, 2, 3, 4, 6, 7, 9]
After step 1, the houses are [1, 2, 3, 4, 7, 9]; the neighboring house groups are (1, 2, 3, 4), (7), (9)
After step 1, the houses are [1, 2, 4, 7, 9]; the neighboring house groups are (1, 2), (4), (7), (9)
After step 1, the houses are [1, 2, 4, 7]; the neighboring house groups are (1, 2), (4), (7)

How to solve this problem? Looks like union find but I don't know a good implementation.