Codeforces Round 746 (Div. 2)
C
Bakry and Partitioning
Codeforces
1700
原题
← BD →
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Bakry faced a problem, but since he's lazy to solve it, he asks for your help.

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You are given a tree of $n$ nodes, the $i$-th node has value $a_i$ assigned to it for each $i$ from $1$ to $n$. As a reminder, a tree on $n$ nodes is a connected graph with $n-1$ edges.

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You want to delete at least $1$, but at most $k-1$ edges from the tree, so that the following condition would hold:

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  • For every connected component calculate the bitwise XOR of the values of the nodes in it. Then, these values have to be the same for all connected components.
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Is it possible to achieve this condition?

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Input

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Each test contains multiple test cases. The first line contains the number of test cases $t$ $(1 \leq t \leq 5 \cdot 10^4)$. Description of the test cases follows.

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The first line of each test case contains two integers $n$ and $k$ $(2 \leq k \leq n \leq 10^5)$.

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The second line of each test case contains $n$ integers $a_1, a_2, ..., a_n$ $(1 \leq a_i \leq 10^9)$.

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The $i$-th of the next $n-1$ lines contains two integers $u_i$ and $v_i$ ($1 \leq u_i, v_i \leq n$, $u_i\neq v_i$), which means that there's an edge between nodes $u_i$ and $v_i$.

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It is guaranteed that the given graph is a tree.

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It is guaranteed that the sum of $n$ over all test cases doesn't exceed $2 \cdot 10^5$.

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Output

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For each test case, you should output a single string. If you can delete the edges according to the conditions written above, output "YES" (without quotes). Otherwise, output "NO" (without quotes).

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You can print each letter of "YES" and "NO" in any case (upper or lower).

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Note

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It can be shown that the objection is not achievable for first, third, and fifth test cases.

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In the second test case, you can just remove all the edges. There will be $5$ connected components, each containing only one node with value $3$, so the bitwise XORs will be $3$ for all of them.

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In the fourth test case, this is the tree: image.

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You can remove an edge $(4,5)$

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The bitwise XOR of the first component will be, $a_1 \oplus a_2 \oplus a_3 \oplus a_4 = 1 \oplus 6 \oplus 4 \oplus 1 = 2$ (where $\oplus$ denotes the bitwise XOR).

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The bitwise XOR of the second component will be, $a_5 = 2$.

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样例

Input #1
5
2 2
1 3
1 2
5 5
3 3 3 3 3
1 2
2 3
1 4
4 5
5 2
1 7 2 3 5
1 2
2 3
1 4
4 5
5 3
1 6 4 1 2
1 2
2 3
1 4
4 5
3 3
1 7 4
1 2
2 3
Output #1
NO
YES
NO
YES
NO
InputCopy OutputCopy
题目信息
题号
1592C
时间限制
1 s
内存限制
256 MB
标签
位运算
构造
DFS 及类似
动态规划
图论
树

题面与样例版权归 Codeforces 及出题人所有;中文翻译由 AI 生成(CI 管线),如有出入请以原文为准。