マイナビプログラミングコンテスト2021(AtCoder Beginner Contest 201)
E
Xor Distances
AtCoder
⌀ 1694
原题
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Problem Statement

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We have a weighted tree with $N$ vertices. The $i$-th edge connects Vertex $u_i$ and Vertex $v_i$ bidirectionally and has a weight $w_i$.

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For a pair of vertices $(x,y)$, let us define $\text{dist}(x,y)$ as follows:

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  • the XOR of the weights of the edges in the shortest path from $x$ to $y$.
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Find $\text{dist}(i,j)$ for every pair $(i,j)$ such that $1 \leq i \lt j \leq N$, and print the sum of those values modulo $(10^9+7)$.

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What is $\text{ XOR }$? The bitwise $\mathrm{XOR}$ of integers $A$ and $B$, $A\ \mathrm{XOR}\ B$, is defined as follows: When $A\ \mathrm{XOR}\ B$ is written in base two, the digit in the $2^k$'s place ($k \geq 0$) is $1$ if exactly one of $A$ and $B$ is $1$, and $0$ otherwise. For example, we have $3\ \mathrm{XOR}\ 5 = 6$ (in base two: $011\ \mathrm{XOR}\ 101 = 110$).

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Constraints

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  • $2 \leq N \leq 2 \times 10^5$
  • $1 \leq u_i \lt v_i \leq N$
  • $0 \leq w_i \lt 2^{60}$
  • The given graph is a tree.
  • All values in input are integers.
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Input

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Input is given from Standard Input in the following format:

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N
u_1 v_1 w_1
u_2 v_2 w_2
\vdots
u_{N-1} v_{N-1} w_{N-1}

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Output

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Print the sum of $\text{dist}(i,j)$, modulo $(10^9+7)$.

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样例

Input #1
3
1 2 1
1 3 3
Output #1
6
We have $\text{dist}(1,2)=1,$ $\text{dist}(1,3)=3,$ and $\text{dist}(2,3)=2$, for the sum of $6$.
Input #2
5
3 5 2
2 3 2
1 5 1
4 5 13
Output #2
62
Input #3
10
5 7 459221860242673109
6 8 248001948488076933
3 5 371922579800289138
2 5 773108338386747788
6 10 181747352791505823
1 3 803225386673329326
7 8 139939802736535485
9 10 657980865814127926
2 4 146378247587539124
Output #3
241240228
Print the sum modulo $(10^9+7)$.
题目信息
题号
abc201_e
时间限制
3 s
内存限制
1024 MB

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