bzoj3669[Noi2014]魔法森林

#include <iostream>
#include <cstdio>
#include <cstring>
#include <cmath>
#include <algorithm>
#define maxn 150005
#define maxm 100005
#define pi pair<int,int>
#define mp(a,b) make_pair(a,b)
using namespace std;

struct note{
    int u,v,a,b;
}wi[maxm];
int n,m,ans,fa[maxn],son[maxn][2],val[maxn],sm[maxn],sm_id[maxn];
bool rev[maxn];

bool comp(note x,note y){
    if (x.a==y.a) return x.b<y.b;
    return x.a<y.a;  
}

struct date{
    int which(int x){
        return son[fa[x]][1]==x;
    }
    int isroot(int x){
        return son[fa[x]][1]!=x&&son[fa[x]][0]!=x;
    }
    void update(int x){
        sm_id[x]=x,sm[x]=val[x];
        if (son[x][0]&&sm[son[x][0]]>sm[x]) sm[x]=sm[son[x][0]],sm_id[x]=sm_id[son[x][0]];
        if (son[x][1]&&sm[son[x][1]]>sm[x]) sm[x]=sm[son[x][1]],sm_id[x]=sm_id[son[x][1]];
    }
    void pushdown(int x){
        if (rev[x]){
            rev[x]^=1,swap(son[x][1],son[x][0]);
            if (son[x][0]) rev[son[x][0]]^=1;
            if (son[x][1]) rev[son[x][1]]^=1;
        }
    }
    void relax(int x){
        if (!isroot(x)) relax(fa[x]);
        pushdown(x);
    }
    void rotata(int x){
        int y=fa[x],d=which(x),dd=which(y);
        if (!isroot(y)) son[fa[y]][dd]=x; fa[x]=fa[y];
        fa[son[x][d^1]]=y,son[y][d]=son[x][d^1];
        fa[y]=x,son[x][d^1]=y;
        update(y);
    }
    void splay(int x){
        relax(x);
        while (!isroot(x)){
            if (isroot(fa[x])) rotata(x);
            else if (which(x)==which(fa[x])) rotata(fa[x]),rotata(x);
            else rotata(x),rotata(x);
        }
        update(x);
    }
    void access(int x){
        for (int p=0;x;x=fa[x]){
            splay(x);
            son[x][1]=p;
            update(x);
            p=x;
        }
    }
    void make_root(int x){
        access(x);
        splay(x);
        rev[x]^=1;
    }
    void link(int x,int y){
        make_root(x);
        fa[x]=y;
    }
    void cut(int x,int y){
        make_root(x);
        access(y);
        splay(y);
        son[y][0]=fa[x]=0;
        update(y);
    }
    void split(int x,int y){
        make_root(x);
        access(y);
        splay(y);
    }
    int query(int x,int y){
        split(x,y);
        return sm[y];
    }
    pi find(int x,int y){
        split(x,y);
        return mp(sm_id[y],sm[y]);
    }
    int find_root(int x){
        access(x);
        splay(x);
        while (son[x][0]) x=son[x][0];
        return x;
    }
}lct;

int main(){
//    freopen("forest.in","r",stdin);
//    freopen("forest.out","w",stdout);
    memset(rev,0,sizeof(rev));
    memset(fa,0,sizeof(fa));
    memset(son,0,sizeof(son));
    memset(val,0,sizeof(val));
    memset(sm,0,sizeof(sm));
    scanf("%d%d",&n,&m);
    for (int i=1;i<=m;i++) scanf("%d%d%d%d",&wi[i].u,&wi[i].v,&wi[i].a,&wi[i].b);
    sort(wi+1,wi+m+1,comp);
    for (int i=1;i<=n;i++) val[i]=0,lct.update(i);
    ans=maxn;
    pi temp;
    for (int i=1;i<=m;i++){
        int u=wi[i].u,v=wi[i].v;
        if (lct.find_root(u)!=lct.find_root(v)){
            val[n+i]=wi[i].b,lct.update(n+i);
            lct.link(n+i,u),lct.link(n+i,v);
        }else{
            temp=lct.find(u,v);
            if (temp.second<=wi[i].b) continue;
            else{
                int t=temp.first;
                lct.cut(wi[t-n].u,t),lct.cut(wi[t-n].v,t);
                val[n+i]=wi[i].b,lct.update(n+i);
                lct.link(n+i,u),lct.link(n+i,v);
            }
        }
        if (lct.find_root(1)!=lct.find_root(n)) continue;
        int t=lct.query(1,n);
        ans=min(ans,t+wi[i].a);
    }
    if (ans>maxm) printf("-1\n");
    else printf("%d\n",ans);
    return 0;
}