Bzoj3924--Fjoi2015幻想乡战略游戏

#include<bits/stdc++.h>
#define PA pair<int,int>
#define INF 0x3f3f3f3f
#define LL long long
using namespace std;

inline int _max(int a,int b) {return a>b?a:b;}

#define MAXN 100005

int n,m;

int head[MAXN],cnt;
struct Edge{
    int next,to,w;
}e[MAXN<<1];
inline void insert(int a,int b,int c) {
    e[++cnt].next=head[a];head[a]=cnt;e[cnt].to=b;e[cnt].w=c;
    e[++cnt].next=head[b];head[b]=cnt;e[cnt].to=a;e[cnt].w=c;
}

bool vis[MAXN];int sz[MAXN],weight[2];
void FindW(int v,int all) {
    vis[v]=1;sz[v]=0;int mx=0;
    for(int i=head[v];i;i=e[i].next) {
        if(!vis[e[i].to]) {
            FindW(e[i].to,all);
            mx=_max(mx,sz[e[i].to]);sz[v]+=sz[e[i].to];
        }
    }
    sz[v]++;mx=_max(mx,all-sz[v]);
    if(weight[0]>mx) weight[0]=mx,weight[1]=v;
    vis[v]=0;
}
int Anc[MAXN][26],Len[MAXN],To[MAXN],Tdis[MAXN];LL Dis[MAXN][26];
void Comp(int v,int anc,int d) {
    vis[v]=1;sz[v]=0;
    Anc[v][++Len[v]]=anc;Dis[v][Len[v]]=d;
    for(int i=head[v];i;i=e[i].next) {
        if(!vis[e[i].to]) {
            Comp(e[i].to,anc,d+e[i].w);
            sz[v]+=sz[e[i].to];
        }
    }
    sz[v]++;vis[v]=0;
}
void Solve(int w) {
    vis[w]=1;if(sz[w]==1) return;
    for(int i=head[w];i;i=e[i].next) {
        if(!vis[e[i].to]) {
            weight[0]=INF;FindW(e[i].to,sz[e[i].to]);
            To[weight[1]]=e[i].to;Tdis[weight[1]]=e[i].w;
            Comp(weight[1],weight[1],0);
            Solve(weight[1]);
        }
    }
}

LL Vc[MAXN],Cos[MAXN],Scos[MAXN],All;
inline void Modify(int x,int y) {
    All+=y;
    for(int i=Len[x];i;i--) {
        Vc[Anc[x][i]]+=y;
        Cos[Anc[x][i]]+=y*Dis[x][i];
        Scos[Anc[x][i]]+=y*Dis[x][i-1];
    }
}
void Change(int x,int sp,LL v,LL c,int fx) {
    for(int i=Len[x];i;i--) {
        if(Anc[x][i]==sp) return;
        Vc[Anc[x][i]]+=v;
        Cos[Anc[x][i]]+=v*(Dis[x][i]+fx)+c;
        Scos[Anc[x][i]]+=v*(Dis[x][i-1]+fx)+c;
    }
}
LL Query(int v,int d) {
    LL ans,go,s=0;
    for(int i=head[v];i;i=e[i].next) 
        if(Anc[e[i].to][d]&&Vc[Anc[e[i].to][d]]>s) s=Vc[Anc[e[i].to][d]],go=Anc[e[i].to][d];
    if((s<<1)>All) {
        LL t=Vc[v]-Vc[go],c=Cos[v]-Scos[go];
        Change(To[go],v,t,c,Tdis[go]);
        ans=Query(go,d+1);
        Change(To[go],v,-t,-c,Tdis[go]);
        return ans;
    }
    else return Cos[v];
}

int main() {
    scanf("%d%d",&n,&m);
    for(int a,b,c,i=1;i<n;i++) {
        scanf("%d%d%d",&a,&b,&c);
        insert(a,b,c);
    }
    weight[0]=INF;FindW(1,n);
    Comp(weight[1],weight[1],0);
    Solve(weight[1]);
    for(int x,y,i=1;i<=m;i++) {
        scanf("%d%d",&x,&y);
        Modify(x,y);
        printf("%lld\n",Query(Anc[1][1],2));
    }
    return 0;
}