# HDU 3639 SCC Hawk-and-chicken

Source: Internet
Author: User

The SCC is shrunk to count the number of points in each SCC.

Then statistics can reach u the number of points, you can reverse the mapping, and then DFS again statistics.

Finally, it is necessary to open a tag array, because there are heavy edges in the test data, and the result is infinite WA.

`1#include <iostream>2#include <cstdio>3#include <cstring>4#include <algorithm>5#include <vector>6#include <stack>7 using namespacestd;8 9 Const intMAXN = the+Ten;Ten intN, M; Onevector<int>G[MAXN]; A  -stack<int>S; - intPRE[MAXN], LOWLINK[MAXN], SCCNO[MAXN], SZ[MAXN], Dfs_clock, scc_cnt; the  - voidDfsintu) - { -Pre[u] = Lowlink[u] = + +Dfs_clock; + s.push (u); -  +      for(inti =0; I < g[u].size (); i++) A     { at         intv =G[u][i]; -         if(!Pre[v]) -         { - Dfs (v); -Lowlink[u] =min (Lowlink[u], lowlink[v]); -         } in         Else if(!sccno[v]) lowlink[u] =min (Lowlink[u], pre[v]); -     } to  +     if(Pre[u] = =Lowlink[u]) -     { thescc_cnt++; *          for(;;) \$         {Panax Notoginseng             intx =S.top (); S.pop (); -SCCNO[X] =scc_cnt; thesz[scc_cnt]++; +             if(x = = u) Break; A         } the     } + } -  \$ voidFIND_SCC () \$ { -Dfs_clock = scc_cnt =0; -memset (PRE,0,sizeof(pre)); thememset (Sccno,0,sizeof(SCCNO)); -memset (SZ,0,sizeof(SZ));Wuyi      for(inti =0; I < n; i++)if(!Pre[i]) DFS (i); the } -  Wu intSUPPORT[MAXN]; - intINDEG[MAXN]; About BOOLVIS[MAXN]; \$vector<int>G2[MAXN]; -  - intDFS2 (intu) - { A     intAns =Sz[u]; +Vis[u] =true; the      for(inti =0; I < g2[u].size (); i++) -     { \$         intv =G2[u][i]; the         if(Vis[v])Continue; theAns + =DFS2 (v); the     } the     returnans; - } in  the intMain () the { About     intT scanf"%d", &T); the      for(intKase =1; Kase <= T; kase++) the     { thescanf"%d%d", &n, &m); +          for(inti =0; I < n; i++) g[i].clear (); -          while(m--) the         {Bayi             intU, v; scanf"%d%d", &u, &v); the G[u].push_back (v); the         } -  - FIND_SCC (); the  thememset (Indeg,0,sizeof(indeg)); the          for(inti =1; I <= scc_cnt; i++) g2[i].clear (); the          for(inti =0; I < n; i++) -              for(intj =0; J < G[i].size (); J + +) the             { the                 intU = sccno[i], V =Sccno[g[i][j]]; the                 if(U = = v)Continue;94indeg[u]++; the g2[v].push_back (u); the             } the 98         intAns =0; About          for(inti =1; I <= scc_cnt; i++)if(!Indeg[i]) -         {101memset (Vis,false,sizeof(Vis));102Support[i] =DFS2 (i);103Ans =Max (ans, support[i]);104         } the 106printf"Case %d:%d\n", Kase, ans-1);107         BOOLFlag =false;108          for(inti =0; I < n; i++)109         { the             intU =Sccno[i];111             if(!indeg[u] && support[u] = =ans) the             {113                 if(flag) printf (" "); theprintf"%d", i); theFlag =true; the             }117         }118Puts"");119     } - 121     return 0;122}`
code June

HDU 3639 SCC Hawk-and-chicken

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