BZOJ3669 （动态树）

  1 #include <map>
  2 #include <set>
  3 #include <stack>
  4 #include <queue>
  5 #include <cmath>
  6 #include <ctime>
  7 #include <string>
  8 #include <vector>
  9 #include <cstdio>
 10 #include <cstdlib>
 11 #include <cstring>
 12 #include <cassert>
 13 #include <iostream>
 14 #include <algorithm>
 15 #pragma comment(linker,"/STACK:102400000,102400000")
 16 using namespace std;
 17 
 18 #define N 200008             
 19 #define E 400008    
 20 #define LL long long
 21 #define lson l,m,rt<<1
 22 #define rson m+1,r,rt<<1|1 
 23 #define clr(x,v) memset(x,v,sizeof(x));
 24 #define bitcnt(x) __builtin_popcount(x)
 25 #define rep(x,y,z) for (int x=y;x<=z;x++)
 26 #define repd(x,y,z) for (int x=y;x>=z;x--)
 27 const int mo  = 1000000007;
 28 const int inf = 0x3f3f3f3f;
 29 const int INF = 2000000000;
 30 /**************************************************************************/ 
 31 int n,m;
 32 int fa[N],val[N],mx[N],rev[N],c[N][2],st[N];
 33 
 34 struct line{
 35     int u,v,a,b;
 36     bool operator < (const line &k) const{
 37         return a<k.a;
 38     }
 39 }eg[E];
 40 bool isroot(int k){
 41     return c[fa[k]][0]!=k && c[fa[k]][1]!=k;
 42 }
 43 void pushup(int x){
 44     int l=c[x][0],r=c[x][1];
 45     mx[x]=x;
 46     if  (val[mx[l]]>val[mx[x]]) mx[x]=mx[l];
 47     if  (val[mx[r]]>val[mx[x]]) mx[x]=mx[r];
 48 }
 49 void pushdown(int x){
 50     int l=c[x][0],r=c[x][1];
 51     if (rev[x]){
 52         if (l) rev[l]^=1;
 53         if (r) rev[r]^=1;
 54         rev[x]^=1;
 55         swap(c[x][0],c[x][1]);
 56     }
 57 }
 58 void rotate(int x){
 59     int y=fa[x],z=fa[y],l,r;
 60     if (c[y][0]==x) l=0; else l=1; r=l^1;
 61     if (!isroot(y)){
 62         if (c[z][0]==y) c[z][0]=x; else c[z][1]=x;
 63     }
 64     fa[x]=z; fa[y]=x; fa[c[x][r]]=y;
 65     c[y][l]=c[x][r]; c[x][r]=y;
 66     pushup(y); pushup(x);
 67 }
 68 void splay(int x){
 69     int top=0; st[++top]=x;
 70     for (int i=x;!isroot(i);i=fa[i]) st[++top]=fa[i];
 71     while (top) pushdown(st[top--]);
 72     while (!isroot(x)){
 73         int y=fa[x],z=fa[y];
 74         if (!isroot(y)){
 75             if (c[y][0]==x^c[z][0]==y) rotate(x);
 76             else rotate(y);
 77         }
 78         rotate(x);
 79     }
 80 }
 81 void access(int x){
 82     int t=0;
 83     while (x){
 84         splay(x);
 85         c[x][1]=t;
 86         pushup(x);
 87         t=x; x=fa[x];
 88     }
 89 }
 90 void rever(int x){
 91     access(x); splay(x); rev[x]^=1;
 92 }
 93 void link(int u,int v){
 94     rever(u); fa[u]=v;
 95 }
 96 void cut(int u,int v){
 97     rever(u); access(v); splay(v); fa[c[v][0]]=0; c[v][0]=0; pushup(v);
 98 }
 99 int find(int u){
100     access(u); splay(u);
101     while (c[u][0]) u=c[u][0];
102     return u;
103 }
104 int query(int u,int v){
105     rever(u); access(v); splay(v); return mx[v];
106 }
107 
108 int main(){
109     scanf("%d%d",&n,&m);
110     rep(i,1,m) scanf("%d%d%d%d",&eg[i].u,&eg[i].v,&eg[i].a,&eg[i].b);
111     sort(eg+1,eg+m+1);
112     int ans=INF;
113     rep(i,1,m){
114         int u=eg[i].u,v=eg[i].v,a=eg[i].a,b=eg[i].b;
115         int flag=1;
116         if (find(u)==find(v)){
117             int t=query(u,v);
118             if (b<val[t]){
119                 cut(t,eg[t-n].u);
120                 cut(t,eg[t-n].v);
121             }
122             else flag=0;
123         }
124         if (flag) {
125             val[i+n]=b; mx[n+i]=n+i;
126             link(i+n,u); 
127             link(i+n,v);
128         }
129         if (find(1)==find(n)){
130             int t=query(1,n);
131             ans=min(ans,val[t]+a);
132         }
133     }
134     printf("%d\n",ans==INF?-1:ans);
135 }