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Could someone explain their solution to 1000? I couldn't understand what the AC codes were doing.

|num| <= 20 and O(N) passes...

My code:

• Div2-Easy: http://ideone.com/HAhcJC
• Div2-Medium: http://ideone.com/UL5r6t
• Div2-Hard: http://ideone.com/fv4IXx
• Div1-Easy: http://ideone.com/NQ1us4
• Div1-Medium: http://ideone.com/iXDHbE
• Div1-Hard: http://ideone.com/8DmwsC

My solution to Div2 500: O(n^4)

The question can be rephrased as:

"Place the origin the orient the coordinate axes in such a way that you get maximum points on the axes"

So we know that if we have 3 distinct points, then we have can place the axes in such a way that the x-axis lies on 1st two points and the y-axis lies on the 3rd point. (This is because you can always place the coordinate axes in such a way that vertices of a triangle lie on the axes). So iterate over all triplets in O(n^3) and for a particular triplet, check how many points lie on the axes including these 3. The maximum will be the answer. I did a small silly mistake but my code passed the system tests later on. Hence overall complexity = O(n^3 * n) = O(n^4)

Code: http://ideone.com/vdyaTI

Also, what exactly was the solution to Div 2 1000? No one actually solved it so I think it must have been a tough one. cgy4ever's solution suggests that it was DP+Bitmask.

Can anyone explain the solution?

Can someone help me with my D2 500? http://www.textsnip.com/13653a

I couldn't think of the integer-only solution. So instead I do this:

  for (each point p)
     translate all points so that p is at the origin
     for (each transformed point q)
         a = angle of q
         rotate all points by angle 2pi-a, so that q is on an axis
         count number of points on x/y axes using 1e-8 precision

I have a test case it's failing on, so I can figure it out eventually. But just wondering if it is the approach or is it the precision? Thanks!!