The Preliminary Contest for ICPC Asia Shanghai 2019 A. Lightning Routing I

传送门

因为某些原因，所以我就去学了 $LCT$ 维护直径， $LCT$ 维护直径我上一个博客讲得很详细了：传送门

这里维护虚儿子用的是 $multiset$ ，没写可删堆

#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cstring>
#include<cmath>
#include<set>
#include<queue>
using namespace std;
typedef long long ll;
inline int read()
{
    int x=0,f=1; char ch=getchar();
    while(ch<'0'||ch>'9') { if(ch=='-') f=-1; ch=getchar(); }
    while(ch>='0'&&ch<='9') { x=(x<<1)+(x<<3)+(ch^48); ch=getchar(); }
    return x*f;
}
const int N=8e5+7;
const ll INF=1e18;
int n,m;
struct edge {
    int x,y;
}e[N];
namespace LCT {
    int c[N][2],fa[N],sz[N],val[N];
    ll sum[N],lmx[N],rmx[N],mxs[N];
    bool rev[N];
    multiset <ll> H[N],P[N];
    inline void ins(int u,int v) { H[u].insert(lmx[v]); P[u].insert(mxs[v]); }
    inline void del(int u,int v) { H[u].erase(H[u].find(lmx[v])); P[u].erase(P[u].find(mxs[v])); }
    inline ll fir(multiset <ll> &S) { return S.size() ? *S.rbegin() : -INF; }
    inline ll sec(multiset <ll> &S) { return S.size()>1 ? *(++S.rbegin()) : -INF; }
    inline void pushup(int x)
    {
        int &lc=c[x][0],&rc=c[x][1];
        sum[x]=sum[lc]+sum[rc]+val[x];
        ll t=max(0ll,fir(H[x])), L=max(t,rmx[lc])+val[x], R=max(t,lmx[rc])+val[x];
        lmx[x]=max(lmx[lc], sum[lc]+R ); rmx[x]=max(rmx[rc], sum[rc]+L );
        mxs[x]=max( max( rmx[lc]+R , lmx[rc]+L ) , max(mxs[lc],mxs[rc]) );
        mxs[x]=max(mxs[x],fir(P[x])); mxs[x]=max(mxs[x], t+val[x] );
        mxs[x]=max(mxs[x], t+val[x]+sec(H[x]) );
    }
    inline void pushdown(int x)
    {
        if(!x||!rev[x]) return;
        int &lc=c[x][0],&rc=c[x][1]; rev[x]=0;
        swap(lc,rc); swap(lmx[x],rmx[x]);
        if(lc) rev[lc]^=1;
        if(rc) rev[rc]^=1;
    }
    inline void rever(int x) { rev[x]=1; pushdown(x); }
    inline bool noroot(int x) { return (c[fa[x]][0]==x)|(c[fa[x]][1]==x); }
    inline void rotate(int x)
    {
        int y=fa[x],z=fa[y],d=(c[y][1]==x);
        if(noroot(y)) c[z][c[z][1]==y]=x;
        fa[x]=z; fa[y]=x; fa[c[x][d^1]]=y;
        c[y][d]=c[x][d^1]; c[x][d^1]=y;
        pushup(y);
    }
    void push_rev(int x)
    {
        if(noroot(x)) push_rev(fa[x]);
        else pushdown(x);
        pushdown(c[x][0]); pushdown(c[x][1]);
    }
    inline void splay(int x)
    {
        push_rev(x);
        while(noroot(x))
        {
            int y=fa[x],z=fa[y];
            if(noroot(y))
                (c[y][0]==x ^ c[z][0]==y) ? rotate(x) : rotate(y);
            rotate(x);
        } pushup(x);
    }
    inline void access(int x)
    {
        for(int y=0;x;y=x,x=fa[x])
        {
            splay(x); if(y) del(x,y);
            if(c[x][1]) ins(x,c[x][1]);
            c[x][1]=y; pushup(x);
        }
    }
    inline void makeroot(int x) { access(x); splay(x); rever(x); }
    inline int findroot(int x)
    {
        access(x); splay(x); pushdown(x);
        while(c[x][0]) x=c[x][0],pushdown(x);
        splay(x); return x;
    }
    inline void split(int x,int y) { makeroot(x); access(y); splay(y); }
    inline void link(int x,int y)
    {
        makeroot(x); if(findroot(y)==x) return;
        makeroot(y); fa[x]=y; ins(y,x); pushup(y);
    }
    inline void cut(int x,int y)
    {
        makeroot(x);
        if(findroot(y)!=x||fa[y]!=x||c[y][0]) return;
        fa[y]=c[x][1]=0; pushup(x);
    }
    inline void Link(int k) { link(e[k].x,n+k); link(e[k].y,n+k); }
    inline void Cut(int k) { cut(e[k].x,n+k); cut(e[k].y,n+k); }
    inline ll query(int x) { access(x); splay(x); return rmx[x]; }
}
int main()
{
    n=read();
    for(int i=1;i<n;i++)
        e[i].x=read(),e[i].y=read(),LCT::val[n+i]=read();
    for(int i=1;i<n;i++) LCT::Link(i);
    m=read(); char s[7]; int a;
    for(int i=1;i<=m;i++)
    {
        scanf("%s",s); a=read();
        if(s[0]=='Q') printf("%lld\n",LCT::query(a));
        else LCT::Cut(a),LCT::val[n+a]=read(),LCT::Link(a);
    }
    return 0;
}