OK, based on a puzzle from the i paper the other day.
A 10x10 grid has every square visited only once by a chess knight (e.g. each move is 2 squares vertical and 1 square horizontal, or 2 squares horizontal and 1 square vertical) and the squares are marked from 1 to 100 in the order they are visited.
Here is a partial grid:-
41,92,5,58,,,3,,45,26
,,42,,,,,,,
,,99,64,,,23,56,27,
66,,,89,100,,54,,,1
39,,67,,87,60,,62,,
,69,88,95,84,71,76,,,19
,,81,,,,,,,
,9,,83,,,,,,49
37,,11,,35,78,73,16,,30
,13,,,,,,31,50,
It has a unique solution (that therefore can be deduced by logic alone, no guessing required).
My puzzle questions are:-
a) What is the most number of squares in the above partial grid (currently containing a number) that can be blanked and the grid can still be solved uniquely?
b) What is the highest total of numbers that can be removed and the grid still have a single unique solution?
[ I haven't got the answers yet but I know that removing at least a few numbers is possible. ]
Use spoilers as appropriate please...