I am not sure what this question has to do with the previous comment and why it is not asked in a separate thead! am I missing a point in your question? Back t

I am not sure what this question has to do with the previous comment and why it is not asked in a separate thead! am I missing a point in your question? Back to your question. There are two types of solutions: 1- Perfect solution, you get a green notification when you find the solution, in which other squares with no number have zero threats. Pressing the 'solution' button reveal the perfect solution 2- Imperfect solution, you get a yellow notification when you find one, in which other squares with no number may be under one or more threats. As a simple example, for the puzzle below placing pawn on c2 is an imperfect solution but placing it on a2 is the perfect solution. https://chedoku.com/#gid=3&d=1& https://chedoku.com/#gid=3&d=1& Is perfect solution in my terminology is what you mean by efficiency solution?