bzoj3669 魔法森林(NOI 2014)

對於每條邊，新建一個點連向2個端點。。。。再排序加邊

/**************************************************************
    Problem: 3669
    User: Clare
    Language: C++
    Result: Accepted
    Time:4740 ms
    Memory:9284 kb
****************************************************************/
 
#include <cstdio>
#include <iostream>
#include <algorithm>
#include <cstring>
#include <cmath>
#include <stack>
#include <queue>
#include <vector>
using namespace std;
 
#define N 200010
#define INF 0x7fffffff
 
int n,m,Ans;
int size[N],fa[N],c[N][2],Max[N],v[N];
struct Node{
    int u,v,a,b;
    bool operator < (const Node &t) const{
        return a==t.a?b<t.b:a<t.a;
    }
}A[N];
bool Rev[N];
stack<int> st;
 
inline int read()
{
    int x=0,f=1;char ch=getchar();
    while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}
    while(ch<='9'&&ch>='0'){x=x*10+ch-'0';ch=getchar();}
    return x*f;
}
 
bool Pd_root(int k)
{
    return !(c[fa[k]][0]==k)&&!(c[fa[k]][1]==k);
}
 
void Pushup(int k)
{
    int l=c[k][0],r=c[k][1];
    Max[k]=k;
    if(v[Max[k]]<v[Max[l]])Max[k]=Max[l];
    if(v[Max[k]]<v[Max[r]])Max[k]=Max[r];
}
 
void Pushdown(int k)
{
    int l=c[k][0],r=c[k][1];
    if(Rev[k])
    {
        Rev[k]^=1;Rev[r]^=1;Rev[l]^=1;
        swap(c[k][0],c[k][1]);
    }
}
 
void Rotate(int x)
{
    int y=fa[x],z=fa[y],l,r;
    if(c[y][0]==x)l=0;else l=1;r=l^1;
    if(Pd_root(y));
    else if(c[z][0]==y)c[z][0]=x;
    else c[z][1]=x;
    fa[x]=z;fa[y]=x;fa[c[x][r]]=y;
    c[y][l]=c[x][r];c[x][r]=y;
    Pushup(y);Pushup(x);
}
 
void Splay(int x)
{
    int i;
    for(i=x;!Pd_root(i);i=fa[i])
        st.push(i);
    st.push(i);
    while(!st.empty())
    {
        int now=st.top();st.pop();
        Pushdown(now);
    }
    while(!Pd_root(x))
    {
        int y=fa[x],z=fa[y];
        if(!Pd_root(y))
        {
            if(c[y][0]==x^c[z][0]==y)
                Rotate(x);
            else Rotate(y);
        }
        Rotate(x);
    }
}
 
void Access(int x)
{
    for(int t=0;x;t=x,x=fa[x])
        Splay(x),c[x][1]=t,Pushup(x);
}
 
void Move_to_root(int x)
{
    Access(x);Splay(x);Rev[x]^=1;
}
 
void Join(int x,int y)
{
    Move_to_root(x);fa[x]=y;Splay(x);
}
 
void Cut(int x,int y)
{
    Move_to_root(x);Access(y);Splay(y);
    if(c[y][0]==x)
        fa[x]=c[y][0]=0;
    else fa[x]=c[y][1]=0;
    Pushup(y);Pushup(x);
}
 
void Split(int x,int y)
{
    Move_to_root(x);Access(y);Splay(y);
}
 
int Find_root(int x)
{
    Access(x);Splay(x);
    while(c[x][0])
        x=c[x][0];
    return x;
}
 
int main()
{
    n=read();m=read();Ans=INF;
    for(int i=1;i<=n;i++)
        Max[i]=i;
    for(int i=1;i<=m;i++)
    {
        A[i].u=read();A[i].v=read();A[i].a=read();A[i].b=read();
    }
    sort(A+1,A+m+1);
    for(int i=1;i<=m;i++)
    {
        if(Find_root(A[i].u)==Find_root(A[i].v))
        {
            Split(A[i].u,A[i].v);
            int t=Max[A[i].v];
            if(v[t]>A[i].b)
            {
                Cut(t,A[t-n].u);Cut(t,A[t-n].v);
                v[n+i]=A[i].b;Max[n+i]=n+i;
                Join(n+i,A[i].u);Join(n+i,A[i].v);
                if(Find_root(1)==Find_root(n))
                {
                    Split(1,n);
                    Ans=min(Ans,A[i].a+v[Max[n]]);
                }
            }
            else continue;
        }
        else
        {
            v[n+i]=A[i].b;Max[n+i]=n+i;
            Join(n+i,A[i].u);Join(n+i,A[i].v);
            if(Find_root(1)==Find_root(n))
            {
                Split(1,n);
                Ans=min(Ans,A[i].a+v[Max[n]]);
            }
        }
    }
    if(Ans==INF)
        cout<<"-1"<<endl;
    else cout<<Ans<<endl;
    return 0;
}