Your profile picture looks great

I think my F would be a little better than std.
The beauty of this problem lies in $$$f(x,x)$$$. It is not difficult to find that the closer the point to $$$x$$$, the more times the point is repeated, and the different $$$x$$$, the different times each edge is repeated ~~ (isn't it obvious) . So we can actually figure out the distance between any two points based on this property. Here's an example (in the figure, the red number indicates the number of counts) :

You will find that all the edges are repeated the same number of times except for the number of times that the edges between the two $$$x$$$are repeated, so you can consider the inclusion repulsion, which is actually $$$dis_{x_1,x_1}+dis_{x_2,x_2}-2 \times dis_{x_1,x_2}$$$. This should make sense, and when you're done, you actually find that the point between the two $$$x$$$has been calculated exactly $$$n$$$. In fact, it is easy to prove that for $$$2 \times dis_{x_1,x_2}$$$the middle of the two $$$x$$$must not be counted because it is already looped, And then $$$dis_{x_1,x_1}+dis_{x_2,x_2}$$$actually understands that every point is on the edge between these two $$$x$$$, so repeat the $$$n$$$ calculation. So we've figured out the distance between any two points, and now we want to generate a tree, and in order to satisfy the distance that we figured out before, we need to minimize each edge, so we need to minimize the spanning tree.

I really enjoyed this one, I'm a big fan of dX!! Although I didn't play this game, I like E and D very much. Personally, I think the difficulty of E is much less than that of D. It may also be my math problem.

Personally, I think the problems F are not very difficult. They are very good. They do not involve advanced algorithms, but simple thinking problems

I really want to see Jiangly vs. tourist too

Personally, I think this E is very good. I can use BIT or segment tree, or even deduce the expression O(n) directly. I really like this problem

omg green round

Good round, the difficulty of div2 is very moderate, very suitable for a novice like me, the E questions are not too difficult, I love it!!!

I don't quite understand why there are many difficult questions to read recently, such as the D question, which is difficult to understand, but I can quickly pass after understanding

so unlucky

blue meow come and kiss

退钱退钱！！！推rating！！！

I don't know why this happened, I was in jail for an hour, what a fuck!!!

Thanks

Is there anyone E using bitset or set to do it, ask for a code

How long does it take to increase the rating?

How long does it take to increase the rating???

SO cool！

What a nice photo！