Cable TV Network vertex connectivity (maximum flow algorithm)

Cable TV Network

Abstract: Give a graph with n points vertex, give M edge. Find the point of connectivity K

Algorithm: Each vertex v is split into V ' V ', and V '-->v ' has a capacity of 1.    For edges in the original (u,v) edge u '--->v ' V '-->u '. P (u,v) for each pair of points, with u as source and V as meeting point.

We just need to fix one vertex and enumerate the other sinks.

1#include <iostream>2#include <cstdio>3#include <cstring>4#include <cmath>5#include <algorithm>6#include <string>7#include <vector>8#include <Set>9#include <map>Ten#include <stack> One#include <queue> A#include <sstream> -#include <iomanip> - using namespacestd; thetypedefLong LongLL; - Const intINF =0x4fffffff; - Const DoubleEXP = 1e-5; - Const intMS = the; + Const intSIZE =100005; -  + //maximum flow algorithm for vertex connectivity of undirected graphs A  at intCap[ms][ms]; - intFLOW[MS][MS];//to disassemble struct C F into two arrays - intQue[ms]; - intPre[ms]; - intAlpha[ms]; - intQs,qe,nodes; in intn,m; -  to intMax_flow (intSource,intsink) + { -memset (Flow,0,sizeof(flow));//0 Stream starts to increase traffic the       intres=0; *        while(1) $       {Panax NotoginsengQs=qe=0; -que[qe++]=Source; thememset (pre,-1,sizeof(pre));//the pre can play the role of flag at the same time +memset (alpha,-1,sizeof(Alpha)); Aalpha[source]=INF; thepre[source]=-2;//-2 end tag, while avoiding-1, indicating no access +              while(qs<QE) -             { $                   intu=que[qs++]; $                    for(intv=0; v<nodes;v++) -                   { -                         if(pre[v]==-1&&flow[u][v]<Cap[u][v]) the                         { -que[qe++]=v;Wuyipre[v]=u; theAlpha[v]=min (alpha[u],cap[u][v]-flow[u][v]); -                         } Wu                   } -                   if(pre[sink]!=-1) About                   { $                         intk=sink; -                          while(pre[k]>=0) -                         { -flow[pre[k]][k]+=Alpha[sink]; Aflow[k][pre[k]]=-Flow[pre[k]][k]; +k=Pre[k]; the                         } -                          Break; $                   } the             } the             if(pre[sink]==-1)//There is no augmented path the                   returnRes; the             Else -res+=Alpha[sink]; in       } the } the  About intMain () the { the        while(SCANF ("%d%d", &n,&m)! =EOF) the       { +             inta,b,ans=INF; -memset (Cap,0,sizeof(CAP)); thenodes=2*N;Bayi              for(intI=0; i<n;i++) thecap[i][i+n]=1; the              for(intI=0; i<m;i++) -             { -scanf"(%d,%d)",&a,&b); thecap[a+n][b]=cap[b+n][a]=INF; the             } the              for(intv=1; v<n;v++) the             { -ans=min (Ans,max_flow (n,v)); the             } the             if(ans==INF) theans=N;94printf"%d\n", ans); the       } the       return 0; the}

Cable TV Network vertex connectivity (maximum flow algorithm)