Re: Difficult Killer Sudoku 31/7

Quote:

I realised that the 22 cage starting at b2 had to be 123457

With large cages I find it is worth thinking about what is not there as much as what is. For example in the b2 cage it has six cells so there are 3 values not in the cage that must add to 23, and the only 3 unique values for 23 are 6,8 & 9, that makes it easy to know that the values in the cage must be 12345&7. Another example would be the f8 cage (38), it has 6 values so it is missing 3 values that add up to 7, so the cage is missing 1,2 & 4.

Large cages can look difficult and they seem to increase the difficulty rating a lot, but they can be very helpful. When starting a Killer Sudoku puzzle the first thing I do is look for small cages with only 1 or 2 possible combinations and large cages that can be helpful.