BZOJ.3991.[SDOI2015]寻宝游戏(思路 set)

//15412KB   5240MS(Rank8...)
#include <set>
#include <cstdio>
#include <cctype>
#include <algorithm>
//#define gc() getchar()
#define MAXIN 300000
#define gc() (SS==TT&&(TT=(SS=IN)+fread(IN,1,MAXIN,stdin),SS==TT)?EOF:*SS++)
typedef long long LL;
const int N=1e5+5;

int n,Q,Enum,H[N],nxt[N<<1],to[N<<1],len[N<<1],ref[N],dfn[N],Index,dep[N],fa[N],top[N],sz[N],son[N];
LL Ans,dis[N];
std::set<int> st;
char IN[MAXIN],*SS=IN,*TT=IN;

inline int read()
{
    int now=0;register char c=gc();
    for(;!isdigit(c);c=gc());
    for(;isdigit(c);now=now*10+c-'0',c=gc());
    return now;
}
inline void AddEdge(int u,int v,int w)
{
    to[++Enum]=v, nxt[Enum]=H[u], len[Enum]=w, H[u]=Enum;
    to[++Enum]=u, nxt[Enum]=H[v], len[Enum]=w, H[v]=Enum;
}
void DFS1(int x)
{
    int mx=0; sz[x]=1;
    for(int v,i=H[x]; i; i=nxt[i])
        if((v=to[i])!=fa[x])
        {
            fa[v]=x, dep[v]=dep[x]+1, dis[v]=dis[x]+(LL)len[i], DFS1(v), sz[x]+=sz[v];
            if(mx<sz[v]) mx=sz[v], son[x]=v;
        }
}
void DFS2(int x,int tp)
{
    ref[dfn[x]=++Index]=x, top[x]=tp;
    if(son[x])
    {
        DFS2(son[x],tp);
        for(int i=H[x]; i; i=nxt[i])
            if(to[i]!=fa[x]&&to[i]!=son[x]) DFS2(to[i],to[i]);
    }
}
inline int LCA(int u,int v)
{
    while(top[u]!=top[v]) dep[top[u]]>dep[top[v]]?u=fa[top[u]]:v=fa[top[v]];
    return dep[u]<dep[v]?u:v;
}
inline LL Dis(int u,int v)
{
    int lca=LCA(u,v);
    return dis[u]+dis[v]-(dis[lca]<<1);
}

int main()
{
    n=read(), Q=read();
    for(int u,v,i=1; i<n; ++i) u=read(),v=read(),AddEdge(u,v,read());
    DFS1(1), DFS2(1,1);
    st.insert(0), st.insert(N-1), ref[0]=0, ref[N-1]=N;
    int p,las,nxt,pos; LL f;
    std::set<int>::iterator it;
    while(Q--)
    {
        p=read();
        if((it=st.find(dfn[p]))!=st.end()) f=-1ll;
        else f=1ll, st.insert(dfn[p]), it=st.find(dfn[p]);
        las=ref[*(--it)], nxt=ref[*(++++it)];

        if(las)
            if(nxt!=N) Ans+=f*(Dis(p,las)+Dis(p,nxt)-Dis(las,nxt));
            else pos=ref[*(++st.begin())], Ans+=f*(Dis(p,las)+Dis(p,pos)-Dis(las,pos));
        else
            if(nxt!=N) pos=ref[*(++st.rbegin())], Ans+=f*(Dis(p,nxt)+Dis(p,pos)-Dis(nxt,pos));
            else ;
        if(f==-1ll) st.erase(dfn[p]);

        printf("%lld\n",Ans);
    }
    return 0;
}

st.insert(0), st.insert(N);
int p; long long f;
std::set<int>::iterator las,nxt,pos;
while(Q--)
{
    p=read(), las=st.upper_bound(dfn[p]), nxt=las--;
    if(st.count(dfn[p])) f=-1ll, --las;
    else f=1ll;
    if(*nxt!=N)
        if(*las) Ans+=f*(Dis(p,ref[*las])+Dis(p,ref[*nxt])-Dis(ref[*las],ref[*nxt]));
        else ----(pos=st.end()), Ans+=f*(Dis(p,ref[*nxt])+Dis(p,ref[*pos])-Dis(ref[*nxt],ref[*pos]));
    else
        if(*las) ++(pos=st.begin()), Ans+=f*(Dis(p,ref[*las])+Dis(p,ref[*pos])-Dis(ref[*las],ref[*pos]));
        else ;
    if(~f) st.insert(dfn[p]);
    else st.erase(dfn[p]);
    printf("%lld\n",Ans);
}