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Notes on problems other than Codeforces - May 2019

Probe Droids - NAIPC 2018:
The differences of the slopes between lattice points (x, y <= 1e6) can be as small as 1e-12. We can descend along Stern-Brocot Tree to find the closest fraction to a floating point number. Euclidean-like method to find the number of lattice points under a certain line. 
F - Unhappy Hacking - AtCoder ARC 59 Tried to make observation of the DP formula but failed to improve an O(N^3) solution It turns out that the content of the string does not matter. Then we can just calculate the number ways to get a string length of m after n operations and divide it by 2^n since the diferent strings are essentially the same.  More problems to add....

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