BZOJ3669 NOI2014魔法森林

  1 #include<bits/stdc++.h>
  2 using namespace std;
  3 const int N=4e5+10;
  4 int f[N],fa[N],ma[N],pos[N],c[N][2],rev[N],s[N],n,m,ans=2e9,w[N];
  5 struct node{
  6     int x,y,a,b;
  7     bool operator <(const node &b)const{
  8         return a<b.a;
  9     }
 10 }a[N];
 11 bool isroot(int x){return c[fa[x]][0]!=x&&c[fa[x]][1]!=x;}
 12 inline int get(int x){return x==f[x]?x:f[x]=get(f[x]);}
 13 void pushup(int x)
 14 {
 15     if(rev[x])
 16     {
 17         rev[x]^=1;rev[c[x][0]]^=1;rev[c[x][1]]^=1;
 18         swap(c[x][0],c[x][1]);
 19     }
 20     return;
 21 }
 22 void update(int x)
 23 {
 24     ma[x]=w[x];pos[x]=x;
 25     if(ma[c[x][0]]>ma[x])ma[x]=ma[c[x][0]],pos[x]=pos[c[x][0]];
 26     if(ma[c[x][1]]>ma[x])ma[x]=ma[c[x][1]],pos[x]=pos[c[x][1]];
 27     return;
 28 }
 29 void rotate(int x)
 30 {
 31     int y=fa[x],z=fa[y],l,r;
 32     l=c[y][1]==x;r=l^1;
 33     if(!isroot(y))c[z][c[z][1]==y]=x;
 34     fa[x]=z;fa[y]=x;fa[c[x][r]]=y;
 35     c[y][l]=c[x][r];c[x][r]=y;
 36     update(y);update(x);
 37 }
 38 void splay(int x)
 39 {
 40     int top=0,i;
 41     for(i=x;!isroot(i);i=fa[i])s[++top]=i;s[++top]=i;
 42     for(;top;top--)pushup(s[top]);
 43     while(!isroot(x))
 44     {
 45         int y=fa[x],z=fa[y];
 46         if(!isroot(y))
 47         {
 48             if(c[y][0]==x^c[z][0]==y)rotate(x);
 49             else rotate(y);
 50         }
 51         rotate(x);
 52     }
 53     return;
 54 }
 55 void access(int x)
 56 {
 57     int y=0;
 58     while(x)
 59     {
 60         splay(x);
 61         c[x][1]=y;
 62         y=x;x=fa[x];
 63     }
 64 }
 65 void mroot(int x)
 66 {
 67     access(x);splay(x);rev[x]^=1;
 68 }
 69 void link(int x,int y)
 70 {
 71     mroot(x);fa[x]=y;splay(x);
 72 }
 73 void cut(int x,int y)
 74 {
 75     mroot(x);access(y);splay(y);c[y][0]=fa[x]=0;
 76 }
 77 int main()
 78 {
 79     scanf("%d%d",&n,&m);
 80     for(int i=1;i<=n+m;++i)f[i]=i;
 81     for(int i=1;i<=m;++i)
 82     {
 83         scanf("%d%d%d%d",&a[i].x,&a[i].y,&a[i].a,&a[i].b);
 84     }
 85     sort(a+1,a+1+m);
 86     for(int i=1;i<=m;++i)
 87     {
 88         w[i+n]=a[i].b;
 89     }
 90     for(int i=1;i<=m;++i)
 91     {
 92         if(a[i].x==a[i].y)continue;
 93         int fx=get(a[i].x),fy=get(a[i].y);
 94         if(fx!=fy)
 95         {
 96             link(a[i].x,i+n);link(i+n,a[i].y);
 97             f[fx]=fy;
 98         }
 99         else
100         {
101             mroot(a[i].x);access(a[i].y);
102             splay(a[i].y);int tmp=pos[c[a[i].y][0]];
103             if(w[tmp]>a[i].b)
104             {
105                 cut(tmp,a[tmp-n].x);cut(tmp,a[tmp-n].y);
106                 link(a[i].x,n+i);link(a[i].y,n+i);
107             }
108         }
109         if(get(1)==get(n))
110         {
111             mroot(1);
112             access(n);
113             splay(n);
114             ans=min(ans,a[i].a+ma[c[n][0]]);
115         }
116     }
117     if(ans!=2e9)
118     printf("%d\n",ans);
119     else puts("-1");
120     return 0;
121 }