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# Prevent a square

## Question

Suppose there are nine points located at (0,0) ; (1,0) ; (2,0) ; (0,1) ; (1,1) ; (2,1) ; (0,2) ; (1,2); (2,2)

Your opponent lets you move first.  You are to remove the fewest amount of points necessary to prevent your opponent from forming a square.  On their turn, they will be adding two points at a location of their choosing to build a square (if they can).

What is the least amount of points, and which ones are they, that you should remove.

## Recommended Posts

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Spoiler

Remove 7 points, leaving any corner point with a non-adjacent edge point.

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These are just some questions for clarification.

1. Can your opponent put a point on a spot that is not one of the original locations?

2. Does the square have to be straight, or can it be tilted?

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Spoiler

xxx       x.x

xxx   ->  ...

xxx       x.x

x means  a coin

. means  coin removed

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22 hours ago, Buddyboy3000 said:

On 6/10/2016 at 9:56 AM, Logophobic said:
Hide contents

Can't delete my post.

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