No.898 tri-βutree
Note
Problem B (tri-βutree), Problem E (K-ary εxtrεεmε), Problem F (Query ζone) are problems in which each is, in this order, a strict generalization of the previous one.Problem Statement
2019/10/4 21:46 The problem statement was corrected.
The town where niuez lives has a certain tradition.
From a tree growing in the town, a piece as small as possible containing $3$ auspicious vertices is cut out and made into a "three-tree offering (mitsugimono)" (tri-butree) to the sacred tree.
There is an undirected tree with $N$ vertices numbered from $0$ to $N-1$ and $N-1$ edges. The $i \ (0 \leq i < N-1)$-th edge has endpoints $u_i$ and $v_i$ and has weight $w_i$.
Process the following $Q$ ${\rm query}$s.
-
$x \ y \ z$
- Among the connected components of the tree, find the total weight of the edges contained in the connected subgraph of the tree that contains the mutually distinct vertices $x, y, z$ and has the minimum number of vertices (2019/10/4 21:44 A terminology error was corrected).
- It can be proved that such a connected subgraph of the tree is uniquely determined.
Input
$N$
$u_0 \ v_0 \ w_0$
$\cdots$
$u_{N-2} \ v_{N-2} \ w_{N-2}$
$Q$
$x_0 \ y_0 \ z_0$
$\cdots$
$x_{Q-1} \ y_{Q-1} \ z_{Q-1}$
- $3 \leq N \leq 10^5$
- $0 \leq u_i, v_i < N$
- $u_i \neq v_i$
- $(u_i, v_i) = (u_j, v_j) \Leftrightarrow i = j$
- $1 \leq w_i < 10^9$
- $1 \leq Q \leq 10^5$
- $0 \leq x_i, y_i, z_i < N$
- $x_i, y_i, z_i$ are mutually distinct
- All inputs are integers
Output
Output $Q$ lines. On the $i$-th line, output the answer to the $i$-th ${\rm query}$ as an integer.
Sample
Sample 1
Input
7 0 1 1 0 2 2 1 3 3 1 4 4 2 5 5 2 6 6 3 0 1 2 0 3 4 3 5 6
Output
3 8 17
In the first query, the connected component with the minimum number of vertices is the one consisting of vertices $0, \ 1, \ 2$.
The total weight of the edges contained in that connected component is $1+2=3$.
In the next query, it is the connected component consisting of vertices $0, \ 1, \ 3, \ 4$.
The total weight of the edges contained in it is $1+3+4=8$.
In the third query, it is the connected component consisting of vertices $0, \ 1, \ 2, \ 3, \ 5, \ 6$.
The total weight of the edges contained in it is $1+3+2+5+6=17$.
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Lemma299