Poj1966cable TV network--min cut (maximum flow)

Title: http://poj.org/problem?id=1966

A point is split into points and out points, with a side right of 1 side, run the maximum flow is the smallest cut;

The original Benquan is assigned to the INF anti-cut;

Enumerating the source and sink points, two directly adjacent points do not have to be enumerated;

Note: 1, the source point is the out point of the enumeration point I, the meeting point is the entry point of the enumeration point J;

2, read in the way, free of space;

3, in the Dinic run the maximum flow process, will change the edge right, so each enumeration to replicate a group of side run maximum flow, so as not to affect the back;

Another: The points in the data start from 0, so the read-in time + + to use.

The code is as follows:

#include <iostream>#include<cstdio>#include<cstring>#include<queue>using namespaceStd;queue<int>Q;intn,m,head[ the],cur[ the],ct=1, inf=1e9,ans,d[ the];BOOLsid[ -][ -];structn{intto,next,w; N (intt=0,intn=0,intww=0): to (T), Next (N), W (WW) {}}edge[6005],ed[6005];voidAddintXintYintz) {ed[++ct]=n (y,head[x],z); head[x]=CT; ed[++ct]=n (X,head[y],0); head[y]=CT;}BOOLBFsintSintt) {memset (d,0,sizeofd);  while(Q.size ()) Q.pop (); D[s]=1; Q.push (s);  while(Q.size ()) {intx=Q.front (); Q.pop ();  for(intI=head[x];i;i=Edge[i].next) {            intu=edge[i].to; if(!d[u]&&EDGE[I].W) {D[u]=d[x]+1;            Q.push (U); }        }    }    returnd[t];}intDfsintXintFintt) {    if(x==t)returnF; intres=0;  for(intI=cur[x];i;i=Edge[i].next) {        intu=edge[i].to; if(d[u]==d[x]+1&&EDGE[I].W) {            intTmp=dfs (U,min (edge[i].w,f-res), T); EDGE[I].W-=tmp; Edge[i^1].w+=tmp; Res+=tmp; if(EDGE[I].W) cur[x]=i; if(res==f)returnF; }    }    if(!res) d[x]=0; returnRes;}intDinic (intSintt) {memcpy (edge,ed,sizeofED);//!!!    intres=0;  while(BFS (s+n,t)) {         for(intI=0; i<=2*n;i++) cur[i]=Head[i]; Res+=dfs (s+n,inf,t); }    returnRes;}intMain () { while(SCANF ("%d%d", &n,&m) = =2)    {        if(!n| | n==1) {printf ("%d\n", N); Continue; }        if(!m) {printf ("0\n"); Continue; } CT=1; ans=inf; memset (Head,0,sizeofhead); memset (SID,0,sizeofSID);  for(intI=1; i<=n;i++) Add (I,i+n,1);//Char dc=0;         for(intI=1; i<=m;i++)        {//dc=0;//while (dc!= ' (') scanf ("%c", &DC);            intx, y; scanf ("(%d,%d)", &x,&y);//or read in the annotated method, here is scanf ("%d,%d", &x,&y);x++;y++;//sid[x][y]=1; sid[y][x]=1; Add (x+N,y,inf); Add (Y+N,x,inf); }         for(intI=1; i<=n;i++)             for(intj=i+1; j<=n;j++)                if(!sid[i][j]) ans=min (ans,dinic (i,j)); if(Ans==inf) ans=N; printf ("%d\n", ans);//dc=0;//While (dc!= ') ') scanf ("%c", &DC);    }    return 0;}

Poj1966cable TV network--min cut (maximum flow)