Problem F:
You are given a tree T that consists of N nodes. Each node is numbered from 1 to N, and node 1 is always the root node of T. Consider the following two operations on T:
- M v: (Mark) Mark node v.
- Q v: (Query) Print the index of the nearest marked ancestor of node v which is nearest to it. Initially, only the root node is marked.
Your job is to write a program that performs a sequence of these operations on a given tree and calculates the value that each Q operation will print. To avoid too large output file, your program is requested to print the sum of the outputs of all query operations. Note that the judges confirmed that it is possible to calculate every output of query operations in a given sequence.
Input
The input consists of multiple datasets. Each dataset has the following format:
The first line of the input contains two integers N and Q, which denotes the number of nodes in the tree T and the number of operations, respectively. These numbers meet the following conditions: 1 ≤ N ≤ 100000 and 1 ≤ Q ≤ 100000.
The following N - 1 lines describe the configuration of the tree T. Each line contains a single integer pi (i = 2, ... , N), which represents the index of the parent of i-th node.
The next Q lines contain operations in order. Each operation is formatted as "M v" or "Q v", where v is the index of a node.
The last dataset is followed by a line containing two zeros. This line is not a part of any dataset and should not be processed.
Output
For each dataset, print the sum of the outputs of all query operations in one line.
Sample Input
6 3
1
1
2
3
3
Q 5
M 3
Q 5
0 0
Output for the Sample Input
4
题目大意:
题目翻译起来比较简单这里不再赘述, 最终就是查询树上几个距离当前查询节点最近的被标记的祖先编号的和。
解题思路:
一开始写dfs,后来才发现是一道很好的并查集的题能想到的真的很厉害(然而我其实没看出来)。代码也很简单就在此记录一下,希望自己以后也能有好思路【。 注意一下因为是求和所以答案会比较大。
代码:
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