AC日记——825G - Tree Queries

825G - Tree Queries

思路：

　　神题，路径拆成半链；

代码：

#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
using namespace std;
#define maxn 1000005
#define INF 0x3f3f3f3f
int n,m,val[maxn],head[maxn],E[maxn<<],V[maxn<<];
int cnt,root,last,ans=INF;
inline void in(int &now)
{
    char Cget=getchar();now=;
    while(Cget>''||Cget<'') Cget=getchar();
    while(Cget>=''&&Cget<='')
    {
        now=now*+Cget-'';
        Cget=getchar();
    }
}
void dfs(int now,int fa,int Min)
{
    val[now]=min(now,Min),Min=min(now,Min);
    for(int i=head[now];i;i=E[i])
    {
        if(fa==V[i]) continue;
        dfs(V[i],now,Min);
    }
}
int main()
{
    //freopen("data.txt","r",stdin);
    in(n),in(m);int u,v;
    for(int i=;i<n;i++)
    {
        in(u),in(v);
        E[++cnt]=head[u],V[cnt]=v,head[u]=cnt;
        E[++cnt]=head[v],V[cnt]=u,head[v]=cnt;
    }
    in(root),in(root),root=root%n+,dfs(root,,INF);
    for(int i=;i<m;i++)
    {
        in(u),in(v);
        v=(last+v)%n+;
        if(u==) ans=min(val[v],ans);
        if(u==) last=min(ans,val[v]),printf("%d\n",last);
    }
    return ;
}