witzar

OK, I made a mistake here: I missed 'X' on hole 1 day 4. It should be: Holes: 1 2 3 4 5 Day1 : - ! - - - Day2 : X - ! - - Day3 : - X - ! - Day4 : X ! X - X Day5 : X X ! X - Day6 : X X X ! X So 6 days is enough. On Day 4 you can check hole 4 instead of hole 2 due to symmetry of X-es and continue by analogy. You can also start with hole 4 instead hole 2 on day 1. This gives total of 4 optimal solutions.