# HDU 2242 Entrance Examination Road boundless-air-conditioning classroom (double connected entry)

Source: Internet
Author: User

`1 /**********************************************************2 Title: Entrance Examination Road boundless--air-conditioning classroom (HDU 2242)3 Links:http://acm.hdu.edu.cn/showproblem.php?pid=22424 algorithm: Double unicom5 idea: Find the bridge and then calculate the difference on both sides of the bridge, on the side of the bridge6 the value is compressed to the number adjacent to the other side. 7 8 ***********************************************************/9 Ten#include <cstdio> One#include <iostream> A#include <cstring> -#include <algorithm> -#include <vector> the#include <stack> - using namespacestd; -  - Const intmx=100005; + intA[MX]; -stack<int>s; +vector<int>G[MX]; A intFlag,dfs_cut; at intDFN[MX],LOW[MX],VS[MX]; - intans,sum; -  - voidInit (intN) - { -     inti; insum=0; -      for(i=0; i<n;i++) to     { + g[i].clear (); -scanf"%d",&a[i]); thesum+=A[i]; *     } \$memset (DFN,0,sizeof(DFN));Panax Notoginsengmemset (Low,0,sizeof(Low)); -Memset (VS,0,sizeof(VS)); theflag=dfs_cut=0; +ans=sum; A } the  + voidDfsintUintFA) - { \$dfn[u]=low[u]=++Dfs_cut; \$vs[u]=1; - s.push (u); -     intp=1;///Go heavy the      for(intI=0; I<g[u].size (); i++) -     {Wuyi  the         intv=G[u][i]; -         if(v==fa&&p) Wu         { -p=0; About             Continue; \$         } -         if(!Vs[v]) -         { - DFS (v,u); Alow[u]=min (low[u],low[v]); +             if(Low[v]>dfn[u])///judging the bridge the             { -flag=1; \$                 inttemp=0, X; the                  the                 ///to compress the bridge once again the                  while(1) the                 { -x=s.top (); in S.pop (); thetemp+=A[x]; the                     if(X==V) Break; About                 } theAns=min (Ans,abs (sum-2*temp)); thea[u]+=temp; the             } +  -         } the         Elselow[u]=min (low[u],dfn[v]);Bayi     } the } the  - intMain () - { the     intn,m; the      while(~SCANF ("%d%d",&n,&m)) the     { the Init (n); -          while(m--) the         { the             intu,v; thescanf"%d%d",&u,&v);94 G[u].push_back (v); the g[v].push_back (u); the         } theDfs0,-1);98         if(flag) printf ("%d\n", ans); About         Elseprintf"impossible\n"); -     }101}`

HDU 2242 Entrance Examination Road boundless-air-conditioning classroom (double connected entry)

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