Tarjan algorithm + indent: Finding strong connected Components POJ 2186

Strongly connected components: 1309. [HAOI2006] Popular Cattle

★ Import File: cow.in output file: cow.out Simple comparison
Time limit: 1 s memory limit: MB

"Title description"

The desire of every cow is to become one of the most popular cows. Now there are n cows, give you m-pairs of integers (a, B), indicating that cow A

B is popular. This relationship is transitive, and if a thinks B is popular, B thinks C is popular, then bull a also thinks that Ox C is popular. Your task is to find out how many cows are considered popular by all cows.

"Input Format"

Line 1th two integers n,m;

Next m line, two numbers per line, A, B, meaning that A is considered to be welcome (the information given may be repeated, that is, there may be multiple A, b)

"Output Format"

A number, that is, how many cows are considered popular by all cows.

"Sample Input"

3 3
0 S
2 1
2 3

"Sample Output"

1

"Data Range"

10% of Data n<=20,m<=50

30% of Data n<=1000,m<=20000

70% of Data n<=5000,m<=50000

100% of Data n<=10000,m<=50000

1 /*judge can have "cattle by all the cows think is welcome", that is, after the contraction point of the figure of the 0 point is only one, if the figure out of 0 points have multiple, certainly does not meet the situation, find out the point, and then output the strong connected components can be*/2#include <iostream>3 using namespacestd;4#include <cstdio>5#include <cstring>6#include <stack>7 #defineN 100108 #defineM 500109 BOOLIn_stack[n];Ten intLow[n],dfn[n],x,y,n,m,father[n]; One intchudu[n],t=0, topt=0, head[n]; A structedge{ -     intV,last,u; -}edge[m*2]; thestack<int>STA; - intAns[n],begi,en; - intRead () - { +     intsum=0, ff=1; -     Chars; +s=GetChar (); A      while(s<'0'|| S>'9') at     { -         if(s=='-') ff=-1; -s=GetChar (); -     } -      while(s>='0'&&s<='9') -     { insum=sum*Ten+s-'0'; -s=GetChar (); to     } +     returnsum*ff; - } the voidAdd_edge (intUintVintk) * { $edge[k].u=u;Panax Notoginsengedge[k].v=v; -edge[k].last=Head[u]; thehead[u]=K; + } A voidinput () the { +N=read (); m=read (); -      for(intI=1; i<=m;++i) $     { $X=read (); y=read (); - Add_edge (x,y,i); -     } the } - voidTarjan (intu)Wuyi { thelow[u]=dfn[u]=++topt; - sta.push (u); Wuin_stack[u]=true; -      for(intL=head[u];l;l=edge[l].last) About     { $         intv=edge[l].v; -         if(!Dfn[v]) -         { - Tarjan (v); Alow[u]=min (low[u],low[v]); +         } the         Else if(In_stack[v]) -low[u]=min (low[u],dfn[v]); $     } the     if(low[u]==Dfn[u]) the     { theans[++ans[0]]=u; the         intx; -          Do in         { thex=sta.top (); the Sta.pop (); Aboutin_stack[x]=false; thefather[x]=u; the} while(x!=u); the     } + } - voidSuo_dian () the {Bayi      for(intL=1; l<=m;++l) the     { the         if(father[edge[l].v]!=father[edge[l].u]) -         { -chudu[father[edge[l].u]]++; the         } the     } the } the intMain () - { theFreopen ("cow.in","R", stdin); theFreopen ("Cow.out","W", stdout); the input ();94      for(intI=1; i<=n;++i) the     { the         if(!Dfn[i]) the         {98 Tarjan (i); About         } -     }101 Suo_dian ();102     intsum=0, L;103      for(intI=1; i<=ans[0];++i)104       if(chudu[ans[i]]==0) the       {106sum++;107L=Ans[i];108       }109     if(sum>1) printf ("0"); the     Else if(sum==1)111     { thesum=0;113          for(intI=1; i<=n;++i) the           if(father[i]==l) thesum++; theprintf"%d\n", sum);117     }118 fclose (stdin); fclose (stdout);119     return 0; -}

Tarjan algorithm + indent: Finding strong connected Components POJ 2186