【spoj1825】Free tour II


After the success of 2nd anniversary (take a look at problem FTOUR for more details), this 3rd year, Travel Agent SPOJ goes on with another discount tour.

The tour will be held on ICPC island, a miraculous one on the Pacific Ocean. We list N places (indexed from 1 to N) where the visitors can have a trip. Each road connecting them has an interest value, and this value can be negative (if there is nothing interesting to view there). Simply, these N places along with the roads connecting them form a tree structure. We will choose two places as the departure and destination of the tour.

Since September is the festival season of local inhabitants, some places are extremely crowded (we call themcrowded places). Therefore, the organizer of the excursion hopes the tour will visit at most K crowded places(too tiring to visit many of them) and of course, the total number of interesting value should be maximum.

Briefly, you are given a map of N places, an integer K, and M id numbers of crowded place. Please help us to find the optimal tour. Note that we can visit each place only once (or our customers easily feel bored), also the departure and destination places don’t need to be different.


There is exactly one case. First one line, containing 3 integers N K M, with 1 <= N <= 200000, 0 <= K <=M, 0 <= M <= N.

Next M lines, each line includes an id number of a crowded place.

The last (N – 1) lines describe (N – 1) two-way roads connected N places, form a b i, with a, b is the id of 2 places, and i is its interest value (-10000 <= i <= 10000).


Only one number, the maximum total interest value we can obtain.



则对于子树S的结点x\[mx[t]+dis[x](deep[x]+t\leq K)\xrightarrow{update} ans\](若根为黑色处理时将K–,处理完恢复)若按照deep倒序处理每个结点,mx指针now按照升序扫,则\(mx[now-1]\xrightarrow{update} mx[now]\),这样就能得到符合条件的mx[t]的最大值。


  • aa2015年1月7日 下午10:13 回复

    2 0 0
    1 2 1

  • lihs2015年5月1日 上午9:38 回复

    那个应该是t+deep <=k 吧