Unique Rectangle Type 4
This Unique Rectangle technique takes other candidates within the unit into account
- We look for additional candidates in two Unique Rectangle cells again, but this time we ignore the extra candidates and focus on the UR candidates themselves
- If one of the UR candidates is no longer possible in any other cell of a unit that contains both cells with the extra candidates, the other UR candidate can be eliminated from those UR cells
- Consider this example. The candidate 6 cannot be placed anywhere else inside the block, so we cannot delete it from our Unique Rectangle cells
- This means that we need to delete 5
