# Project Euler #166: Criss Cross

# Project Euler #166: Criss Cross

Julia_p + 0 comments please provide explanation for sample output

kunalgupta777 + 0 comments For a given n, there are (n+1)^16 computations to be performed, to find out all matrices possible, clearly TLE, can anyone give a headstart?

jcpince + 0 comments Hi all,

I'm a bit lost and possibly because that's my first time in this kind of problem solving "games" (note that I started with the problem 165 and now tried this problem 166, I didn't go through all the games).

I "solved" this problem by generating the matrices and checking but I can't really consider this solved since with all the caching or improvements I tried, I cannot compute the result for digits above 3 (1 is almost immediate, 2 takes 2 seconds on my laptop and 3 takes around 60s, 4 is exponentially longer and so forth).

I understand that I'm NOT on my way to really solve this! Whatever optimization I could come up with will likely not reduce enough the computation time to address 7.

I tried to read on criss-cross Euler on the web but can't really understand the relationship between the matrices and the polyhedrons faces, edges and vertices.

So, my questions are the following: Should I go through the exercises in order to 'discover' Euler along the path?

- Should I go through the exercises in order to 'discover' Euler along the path?
- This exercise is tagged "Easy", did I miss something completely?
- Is there a paper that I didn't find clarifying the relationship Euler/matrices?

Thanks! JC

xinghe117 + 0 comments I don't get it. How would you make n(1) = 34? you put 4 ones and 12 0s in the 4 by 4, there is only 8 (4*2) unique ways to put them. and if you allow them to be non-unique, then what is the point of this question? Any one has any idea how the base case is calculated?

utsav47 + 0 comments should i try all the combinations? it will exceed time limit

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