| Contests - ACM Student Chapter - PSUT |
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| Private |
| Spectator |
| GJU JCPC Qualification 2026 |
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| Finished |
Abushogi is trying to run away from the police. The city he is in can be represented as a tree consisting of $$$n$$$ intersections (nodes) and $$$n-1$$$ bidirectional roads (edges).
Abushogi is currently at the root of the tree, which is intersection $$$1$$$. He will successfully escape and be considered safe if he can reach any leaf intersection in the city.
An intersection is considered a leaf if it is connected to exactly one other intersection (and is not intersection $$$1$$$).
If the city only has $$$1$$$ intersection, intersection $$$1$$$ is considered a leaf. However, the police have deployed cops at certain intersections. Abushogi cannot pass through or land on any intersection that has a cop stationed there.
If there is a cop at intersection $$$1$$$, Abushogi is instantly caught.Given the layout of the city and the locations of the cops, determine if it is possible for Abushogi to reach a leaf intersection and escape.
The first line contains a single integer $$$t$$$ ($$$1 \le t \le 10^4$$$) — the number of test cases.
The first line of each test case contains a single integer $$$n$$$ ($$$1 \le n \le 2 \cdot 10^5$$$) — the number of intersections.
The second line contains $$$n$$$ integers $$$c_1, c_2, \ldots, c_n$$$ ($$$c_i \in \{0, 1\}$$$). If $$$c_i = 1$$$, there is a cop at intersection $$$i$$$. If $$$c_i = 0$$$, intersection $$$i$$$ is empty.Each of the next $$$n-1$$$ lines contains two integers $$$u$$$ and $$$v$$$ ($$$1 \le u, v \le n, u \ne v$$$) — representing a bidirectional road between intersection $$$u$$$ and intersection $$$v$$$.
It is guaranteed that the given edges form a valid tree, and the sum of $$$n$$$ over all test cases does not exceed $$$2 \cdot 10^5$$$.
For each test case, output "YES" if it is possible for Abushogi to reach a leaf intersection without encountering any cops. Otherwise, output "NO".
In the output, the "YES"s and "NO"s are case-insensitive, meaning that outputs such as "yEs" and "nO" are valid. However, the grid is case-sensitive.
350 0 1 0 01 21 32 42 541 0 0 01 22 33 410
YES NO YES
In the first testcase, intersection 3 has a cop. Abushogi can run $$$1 \rightarrow 2 \rightarrow 4$$$ or $$$1 \rightarrow 2 \rightarrow 5$$$ to escape.
In the second testcase, there is a cop at intersection 1, so he is instantly caught. In the third testcase, the city only has 1 intersection, and it's empty, so he is already safe.
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