bzoj4435: [Cerc2015]Juice Junctions（最小割树+hash）

 1 //minamoto
 2 #include<iostream>
 3 #include<cstdio>
 4 #include<cstring>
 5 #include<cmath>
 6 #include<algorithm>
 7 #define inf 0x3f3f3f3f3
 8 using namespace std;
 9 #define getc() (p1==p2&&(p2=(p1=buf)+fread(buf,1,1<<21,stdin),p1==p2)?EOF:*p1++)
10 char buf[1<<21],*p1=buf,*p2=buf;
11 inline int read(){
12     #define num ch-‘0‘
13     char ch;bool flag=0;int res;
14     while(!isdigit(ch=getc()))
15     (ch==‘-‘)&&(flag=true);
16     for(res=num;isdigit(ch=getc());res=res*10+num);
17     (flag)&&(res=-res);
18     #undef num
19     return res;
20 }
21 const int N=3005;
22 int ver[N<<2],Next[N<<2],edge[N<<2],head[N],tot=1;
23 inline void add(int u,int v,int e){
24     ver[++tot]=v,Next[tot]=head[u],head[u]=tot,edge[tot]=e;
25     ver[++tot]=u,Next[tot]=head[v],head[v]=tot,edge[tot]=e;
26 }
27 int dep[N],q[N],n,m,S,T,ans;
28 bool bfs(){
29     int l=0,r=1;memset(dep+1,-1,sizeof(int)*n);dep[q[0]=S]=0;
30     while(l<r){
31         int u=q[l++];
32         for(int i=head[u];i;i=Next[i])
33         if(dep[ver[i]]<0&&edge[i])
34         dep[ver[i]]=i,q[r++]=ver[i];
35     }
36     return ~dep[T];
37 }
38 int id[N],tmp[N];
39 unsigned Pow=1,Hash[4][N];
40 void solve(int L,int R){
41     if(L==R) return;
42     for(int i=2;i<=tot;i+=2)
43     edge[i]=edge[i^1]=1;
44     S=id[L],T=id[R];int flow=0,j;
45     while(bfs()){
46         ++flow;
47         for(int i=T;i!=S;i=ver[j^1]) --edge[j=dep[i]],++edge[j^1];
48     }
49     Pow*=233;
50     for(int i=1;i<=n;++i)
51     if(~dep[i]) Hash[flow][i]+=Pow;
52     int l=L,r=R;
53     for(int i=L;i<=R;++i)
54     if(~dep[id[i]]) tmp[l++]=id[i];
55     else tmp[r--]=id[i];
56     memcpy(id+L,tmp+L,sizeof(int)*(R-L+1));
57     solve(L,l-1),solve(r+1,R);
58 }
59 int main(){
60     //freopen("testdata.in","r",stdin);
61     n=read(),m=read();
62     for(int i=1,u,v;i<=m;++i)
63     u=read(),v=read(),add(u,v,1);
64     for(int i=1;i<=n;++i) id[i]=i;
65     solve(1,n);
66     for(int i=1;i<=n;++i)
67     for(int j=i+1;j<=n;++j)
68     for(int k=0;k<=3;++k)
69     if(Hash[k][i]!=Hash[k][j]) {ans+=k;break;}
70     printf("%d\n",ans);
71     return 0;
72 }