POJ 3694 Network (bridge Entry)

1 /********************************************2 Network (POJ 3694)3     http://poj.org/problem?id=36944 Bridge Entry question + LCA (the smallest common ancestor in the tree)5 To do this, you have to use the adjacency table (to do this problem to learn), because6 the edge of the given side has a heavy edge, the vector is not good to record the heavy edge. 7 8 ********************************************/9 Ten#include <iostream> One#include <algorithm> A#include <cstring> -#include <cstdio> - using namespacestd; the  - Const intm=100005; -  - structEage///adjacency Table Building Map + { -     intv; +     intNext; A     intvs; at }; -  -Eage eage[m*4]; - intLOW[M],DFN[M],FATHER[M];///Father[i] For the Father node of I - intFLAG[M],VS[M],HEAD[M];///Falg[i] for the side of the Father node of I and I - intdfs_cut,ans,k; in  - voidInit () to { +memset (DFN,0,sizeof(DFN)); -memset (Low,0,sizeof(Low)); thememset (Flag,0,sizeof(flag)); *Memset (VS,0,sizeof(VS)); $memset (head,-1,sizeof(head));Panax Notoginsengdfs_cut=ans=k=0; - } the  + voidAddintUintv) A { theeage[k].v=v; +eage[k].vs=0; -eage[k].next=Head[u]; $head[u]=k++; $ } -  - voidDfsintU///Find a bridge the { -vs[u]=1;Wuyidfn[u]=low[u]=++Dfs_cut; the      for(inti=head[u];i!=-1; i=eage[i].next) -     { Wu         if(!Eage[i].vs) -         { Abouteage[i].vs=eage[i^1].vs=1; $             intv=eage[i].v; -             if(!Vs[v]) -             { -father[v]=u; A Dfs (v); +low[u]=min (low[u],low[v]); the                 if(dfn[u]<Low[v]) -                 { $ans++; theflag[v]=1; the                 } the             } the             Elselow[u]=min (low[u],dfn[v]); -         } in     } the } the  About voidLCA (intUintv) the { the     if(dfn[u]<Dfn[v]) the     { +u^=v; -v^=u; theu^=v;Bayi     } the      while(dfn[u]>Dfn[v]) the     { -         if(Flag[u]) ans--; -flag[u]=0; theu=Father[u]; the     } the      while(u!=v) the     { -         if(Flag[v]) ans--; the         if(Flag[u]) ans--; theflag[u]=0; theflag[v]=0;94v=Father[v]; theu=Father[u]; the     } the }98  About intMain () - {101   //freopen ("C://Users//Administrator//Desktop//in.txt "," R ", stdin);102    //freopen ("C://Users//Administrator//Desktop//OUT.txt "," w ", stdout);103     intn,m,cut=0;104      while(cin>>n>>m) the     {106         if(!n&&!m)return 0;107 Init ();108          for(intI=1; i<=n;i++) father[i]=i;109         intu,v; the          while(m--)111         { theCin>>u>>v;113 Add (u,v); the Add (v,u); the         } theDfs1);117cout<<" Case"<<++cut<<":"<<Endl;118         intQ;119Cin>>Q; -          while(q--)121         {122Cin>>u>>v;123 Lca (u,v);124cout<<ans<<Endl; the         }126cout<<Endl;127     } -     return 0;129}

POJ 3694 Network (bridge Entry)