BZOJ 4326 运输计划

写的巨慢。。。

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#define maxv 300500
#define maxe 600500
using namespace std;
struct edge
{
    int v,w,nxt;
}e[maxe];
struct plans
{
    int u,v,t,d;
}p[maxv];
int n,m,x,y,z,g[maxv],nume=0,dis[maxv][21],anc[maxv][21],dep[maxv],fath_e[maxv];
int d=0,t=0,stack[maxv],top=0,val[maxv];
void addedge(int u,int v,int w) {e[++nume].v=v;e[nume].w=w;e[nume].nxt=g[u];g[u]=nume;}
int read()
{
    int data=0;char ch;
    while (ch<'0' || ch>'9') ch=getchar();
    while (ch>='0' && ch<='9')
    {
        data=data*10+ch-'0';
        ch=getchar();
    }
    return data;
}
void dfs1(int x)
{
    for (int i=g[x];i;i=e[i].nxt)
    {
        int v=e[i].v;
        if (v!=anc[x][0])
        {
            anc[v][0]=x;dis[v][0]=e[i].w;
            dep[v]=dep[x]+1;fath_e[v]=i;
            dfs1(v);
        }
    }
}
void dfs2(int x)
{
    for (int i=g[x];i;i=e[i].nxt)
    {
        int v=e[i].v;
        if (anc[x][0]!=v)
        {
            dfs2(v);
            val[x]+=val[v];
        }
    }
}
void get_dis(int x)
{
    int u=p[x].u,v=p[x].v;
    d=0;t=1;
    if (dep[u]<dep[v]) {swap(u,v);swap(p[x].u,p[x].v);}
    for (int e=20;e>=0;e--)
    {
        if ((dep[anc[u][e]]>=dep[v]) && (anc[u][e]))
        {
            d+=dis[u][e];
            u=anc[u][e];
        }
    }
    if (u==v) {t=u;return;}
    for (int e=20;e>=0;e--)
    {
        if (anc[u][e]!=anc[v][e])
        {
            d+=dis[u][e]+dis[v][e];
            u=anc[u][e];v=anc[v][e];
        }
    }
    t=anc[u][0];d+=dis[u][0]+dis[v][0];
    return;
}
void get_table1()
{
    for (int e=1;e<=20;e++)
        for (int i=1;i<=n;i++)
        {
            anc[i][e]=anc[anc[i][e-1]][e-1];
            dis[i][e]=dis[i][e-1]+dis[anc[i][e-1]][e-1];
        }
}
void get_table2()
{
    for (int i=1;i<=m;i++)
    {
        get_dis(i);
        p[i].t=t;p[i].d=d;
    }
}
void get_labled()
{
    memset(val,0,sizeof(val));
    for (int i=1;i<=top;i++)
    {
        int x=stack[i];
        if (p[x].t==p[x].v) val[p[x].v]--,val[p[x].u]++;
        else val[p[x].t]-=2,val[p[x].u]++,val[p[x].v]++;
    }
}
bool check(int x)
{
    top=0;
    for (int i=1;i<=m;i++)
        if (p[i].d>x)
            stack[++top]=i;
    get_labled();
    dfs2(1);
    int mx=0;
    for (int i=1;i<=n;i++)
    {
        if (val[i]==top) 
            mx=max(mx,e[fath_e[i]].w);
    }
    for (int i=1;i<=top;i++)
    {
        if (p[stack[i]].d-mx>x)
            return false;
    }
    return true;
}
int half_search()
{
    int l=1,r=(n+1)*1000,ans;
    while (l<=r)
    {
        int mid=l+r>>1;
        if (check(mid)) {ans=mid;r=mid-1;}
        else l=mid+1;
    }
    return ans;
}
int main()
{
    n=read();m=read();
    for (int i=1;i<=n-1;i++)
    {
        x=read();y=read();z=read();
        addedge(x,y,z);addedge(y,x,z);
    }
    for (int i=1;i<=m;i++)
        p[i].u=read(),p[i].v=read();
    dfs1(1);
    get_table1();
    get_table2();
    printf("%d\n",half_search());
    return 0;
}