VOCV - Con-Junctions
The city of Y-O is a network of two-way streets and junctions with the following properties:
- There is no more than one street between each pair of junctions.
- Every junction is connected to every other junction either directly via a street or through other junctions by a unique path.
- When a light is placed at a junction, all the streets meeting at this junction are also lit.
A valid lighting is a set of junctions such that if lights were placed at these, all the streets would be lit. An optimal lighting is a valid lighting such that it contains the least number of junctions.
The task is divided into two subtasks:
- Find the number of lights in an optimal lighting.
- Find the total number of such optimal lightings in the city.
- The first line of the input contains a positive integer t <= 20, denoting the number of test cases.
- The description of the test cases follows one after the other.
- Network Description:
- The first line of description of a network consists of a positive integer n <= 100010 denoting the number of junctions in the network.
- Each junction is numbered with a unique integer between 1 and n.
- The following n-1 lines contain a pair of integers u v (1 <= u,v <= n) separated by a single space denoting that there is a street between junction u and junction v.
The output must consist of t lines, the kth line corresponding to the kth network; (1 <= k <= t). The kth line must contain two integers separated by a single space. The first integer on the kth line must be the number of junctions in an optimal lighting of network k. The second integer must be N%10007, which is the remainder left by the number of optimal lightings when divided by 10007.
took some time, dP on tree :)
Writing the bottom up for this problem gives you real essence of DP :)
Note: Don't take mod for first integer in output
Really Nice Problem ;)