Coloring trees

3.4

20 votes
Algorithms, Graphs
Problem

There are N cities that are connected by N1 roads. K cities have bus terminals and other NK cities have bus stops. A bus terminus is a designated place where a bus starts or ends its scheduled route.

A bus should start from a terminal and must end its journey at another terminal visiting any city at most once. A city is crowded if there is a bus service in the city where one or more than one bus visits it along any route. You are required to simulate the routes for the buses so that the maximum number of cities is crowded. You can assume there is a number of buses ready for service from each terminus.

Note:

  • A city with a bus terminal is always crowded.
  • It is guaranteed that it is possible to reach from one city to another city.

Input format

  • First line: Two space-separated integers N and K
  • Next N1 lines: Two integers u and v that denote city u and city v is connected by a road
  • Next line: K integers denoting the cities that have a bus terminal

Output format

Print the number of cities that are crowded after all simulations. 

Constraints

1N200000

1K,u,vN

It is guaranteed that it is possible to reach from one city to another city.

Time Limit: 2
Memory Limit: 256
Source Limit:
Explanation

It is possible to simulate a bus route starting from terminus 1 to terminus 4 or 5 thereby making city 2, a crowded city. But it is impossible to make city 3 crowded.

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