bzoj2718 [Violet 4] Graduation Trip

Description

Input

Output

Maximum number of attractions to choose from

Sample Input7 6
1 2
2 3
5 4
4 3
3 6
6 7

Sample Output2
HINT

The question is the conclusion

Answer = Longest anti-chain = minimum path overlay =n-binary graph Max match

First Floyd to deal with the connectivity between two points, and then split, if a can go to B, a to B ' connected edge

#include <cstdio> #include <iostream> #include <cstring> #define LL long long#define inf 0x7ffffff#    Define S 0#define T 2*n+1using namespace Std;inline ll read () {LL X=0,f=1;char Ch=getchar (); while (ch< ' 0 ' | |    Ch> ' 9 ') {if (ch== '-') F=-1;ch=getchar ();}    while (ch>= ' 0 ' &&ch<= ' 9 ') {x=x*10+ch-' 0 '; Ch=getchar ();} return x*f;} struct Edge{int to,next,v;} E[100010];int n,m,cnt=1,ans;bool go[1010][1010];int head[100010];int q[100010];int h[100010];inline void ins (int u,int    V,int W) {e[++cnt].to=v;    E[cnt].v=w;    E[cnt].next=head[u]; head[u]=cnt;}    inline void Insert (int u,int v,int W) {ins (u,v,w); Ins (v,u,0);}    inline bool BFs () {memset (h,-1,sizeof (h));    Q[1]=s;h[s]=0;int t=0,w=1;        while (t<w) {int now=q[++t];            for (int i=head[now];i;i=e[i].next) if (e[i].v&&h[e[i].to]==-1) {q[++w]=e[i].to;          h[e[i].to]=h[now]+1;    }} if (H[t]==-1) return 0; return 1;} inline int DFs (int x,int f) {if (x==t| |!    f) return F;    int w,used=0; for (int i=head[x];i;i=e[i].next) if (e[i].v&&h[e[i].to]==h[x]+1) {W=dfs (E[i].to,min (f-u            SED,E[I].V));            E[i].v-=w;            E[i^1].v+=w;            Used+=w;        if (used==f) return F;    } if (!used) h[x]=-1; return used;} inline void Dinic () {while (BFS ()) Ans+=dfs (S,inf);}    int main () {n=read (); M=read ();        for (int i=1;i<=m;i++) {int x=read (), Y=read ();    Go[x][y]=1; } for (int k=1;k<=n;k++) for (int i=1;i<=n;i++) for (int j=1;j<=n;j++) if (Go[i][k]&&go[k][j]         ) Go[i][j]=1;         for (int i=1;i<=n;i++) for (int j=1;j<=n;j++) if (Go[i][j]) insert (i,j+n,1);    for (int i=1;i<=n;i++) Insert (s,i,1), insert (i+n,t,1);    Dinic (); printf ("%d\n", N-ans);}

bzoj2718 [Violet 4] Graduation Trip