COGS——C2274. [HEOI 2016] tree

http://www.cogs.pro/cogs/problem/problem.php?pid=2274

★☆   输入文件：heoi2016_tree.in   输出文件：heoi2016_tree.out   简单对比
时间限制：1 s   内存限制：128 MB

福利题?

 #include <algorithm>
 #include <iostream>
 #include <cstdio>

 using namespace std;

 const int N(1e6+);
 int n,q,u,v;

 int mark[N],dad[N];
 int Get_grandfa(int x,int y)
 {
     for(;!mark[x];)
         x=dad[x];
     return x;
 }

 int main()
 {
     freopen("heoi2016_tree.in","r",stdin);
     freopen("heoi2016_tree.out","w",stdout);
     scanf("%d%d",&n,&q);
     for(int i=;i<n;i++)
         scanf("%d%d",&u,&v),dad[v]=u;
     mark[]=;
     for(char op;q--;)
     {
         cin>>op>>v;
         if(op=='C') mark[v]=;
         else printf("%d\n",Get_grandfa(v,));
     }
     return ;
 }