BZOJ 1977 次小生成树

TM终于过了。。。。

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#define maxv 300500
#define maxe 800500
#define inf 0x7fffffffffffffff
using namespace std;
struct edge
{
    long long v,w,nxt;
}e[maxe];
struct edge_mp
{
    long long u,v,w,flag;
}mp[maxe];
long long n,m,g[maxv],nume=,father[maxv],anc[maxv][],mx1[maxv][],mx2[maxv][],ans=,dx=inf,dis[maxv];
long long r1=,r2=;
bool cmp(edge_mp x,edge_mp y)
{
    return x.w<y.w;
}
void addedge(long long u,long long v,long long w)
{
    e[++nume].v=v;
    e[nume].w=w;
    e[nume].nxt=g[u];
    g[u]=nume;
}
long long getfather(long long x)
{
    if (father[x]!=x)
        father[x]=getfather(father[x]);
    return father[x];
}
void kruskal()
{
    for (long long i=;i<=n;i++) father[i]=i;
    sort(mp+,mp+m+,cmp);
    for (long long i=;i<=m;i++)
    {
        long long u=mp[i].u,v=mp[i].v,w=mp[i].w;
        if (getfather(u)!=getfather(v))
        {
            father[getfather(u)]=getfather(v);mp[i].flag=;ans+=w;
            addedge(u,v,w);addedge(v,u,w);
        }
    }
}
void dfs(long long x,long long father)
{
    for (long long i=g[x];i;i=e[i].nxt)
    {
        long long v=e[i].v;
        if (v!=father)
        {
            anc[v][]=x;mx1[v][]=e[i].w;mx2[v][]=;
            dis[v]=dis[x]+;
            dfs(v,x);
        }
    }
}
void get_table()
{
    for (long long e=;e<=;e++)
        for (long long i=;i<=n;i++)
        {
            anc[i][e]=anc[anc[i][e-]][e-];
            long long regis[];
            regis[]=mx1[i][e-];regis[]=mx1[anc[i][e-]][e-];
            regis[]=mx2[i][e-];regis[]=mx2[anc[i][e-]][e-];
            sort(regis+,regis+);
            mx1[i][e]=regis[];
            for (long long j=;j>=;j--)
            {
                if (regis[j]==regis[j+]) continue;
                else {mx2[i][e]=regis[j];break;}
            }
        }
}
 
void get_ans(long long x)
{
    long long u=mp[x].u,v=mp[x].v;r1=-;r2=-;
    long long k1=-,k2=-,k3=-,k4=-;
    if (dis[u]<dis[v]) swap(u,v);
    if (dis[u]!=dis[v])
    {
        for (long long e=;e>=;e--)
        {
            long long pos=anc[u][e];
            if ((dis[pos]>=dis[v]) && (pos>))
            {
                long long regis[];
                regis[]=mx1[u][e];regis[]=mx2[u][e];regis[]=k1;regis[]=k2;
                sort(regis+,regis+);
                k1=regis[];
                for (long long i=;i>=;i--)
                {
                    if (regis[i]==regis[i+]) continue;
                    else {k2=regis[i];break;}
                }
                u=pos;
            }
        }
    }
    if (u==v)
    {
        r1=k1;r2=k2;
        return;
    }
    for (long long e=;e>=;e--)
    {
        long long posu=anc[u][e],posv=anc[v][e];
        if (posu!=posv)
        {
            long long regis[];
            regis[]=mx1[u][e];regis[]=mx2[u][e];regis[]=k1;regis[]=k2;
            sort(regis+,regis+);
            k1=regis[];
            for (long long i=;i>=;i--)
            {
                if (regis[i]==regis[i+]) continue;
                else {k2=regis[i];break;}
            }
            regis[]=mx1[v][e];regis[]=mx2[v][e];regis[]=k3;regis[]=k4;
            sort(regis+,regis+);
            k3=regis[];
            for (long long i=;i>=;i--)
            {
                if (regis[i]==regis[i+]) continue;
                else {k4=regis[i];break;}
            }
            u=posu;v=posv;
        }
    }
    long long regis[];
    regis[]=k1;regis[]=k2;regis[]=k3;regis[]=k4;regis[]=mx1[u][];regis[]=mx1[v][];
    sort(regis+,regis+);
    r1=regis[];
    for (long long i=;i>=;i--)
    {
        if (regis[i]==regis[i+]) continue;
        else {r2=regis[i];break;}
    }
}
int main()
{
    scanf("%lld%lld",&n,&m);
    for (long long i=;i<=m;i++)
    {
        scanf("%lld%lld%lld",&mp[i].u,&mp[i].v,&mp[i].w);
        mp[i].flag=;
    }
    kruskal();
    memset(mx1,,sizeof(mx1));
    memset(mx2,,sizeof(mx2));
    dfs(,);
    get_table();
    for (long long i=;i<=m;i++)
    {
        if (mp[i].flag) continue;
        long long u=mp[i].u,v=mp[i].v,w=mp[i].w;
        get_ans(i);
        if (r1==mp[i].w)
        {
            if (r2==-) continue;
            dx=min(dx,mp[i].w-r2);
        }
        else if (r1<mp[i].w) dx=min(dx,mp[i].w-r1);
    }
    printf("%lld\n",ans+dx);
    return ;
}