BZOJ1051 [HAOI2006] Popular Cattle

Title Link: http://www.lydsy.com/JudgeOnline/problem.php?id=1051

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, a, b), indicating that cow A is considered to be 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

The first line is two numbers 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

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

Review Tarjan template, Tarjan after the contraction point, if there is only a 0 of the strong Unicom component output its size, otherwise no solution

1#include <iostream>2#include <cstdio>3#include <algorithm>4#include <cstring>5#include <stack>6 #defineRep (i,l,r) for (int i=l; i<=r; i++)7 #defineCLR (x, y) memset (x,y,sizeof (×))8 #defineTravel (x) for (int i=last[x]; i; i=edge[i].pre)9 using namespacestd;Ten Const intINF =0x3f3f3f3f; One Const intMAXN =10010; A structedge{ -     intpre,to; -}edge[50010]; the intn,m,x,y,tot=0, ans,scc=0, dfsclock=0, LAST[MAXN],DFN[MAXN],LOW[MAXN],BELONG[MAXN],CNT[MAXN]; - BOOLISIN[MAXN],OUD[MAXN]; -Stack <int>s; -InlineintRead () { +     intAns =0, F =1; -     Charc =GetChar (); +      while(!IsDigit (c)) { A         if(c = ='-') F =-1; atc =GetChar (); -     } -      while(IsDigit (c)) { -Ans = ans *Ten+ C-'0'; -c =GetChar (); -     } in     returnAns *F; - } toInlinevoidAddedge (intXinty) { +Edge[++tot].pre =Last[x]; -Edge[tot].to =y; theLAST[X] =tot; * } $ voidTarjan (intx) {Panax NotoginsengDFN[X] = low[x] = + +Dfsclock; -ISIN[X] =1; S.push (x); the Travel (x) { +         if(!Dfn[edge[i].to]) { A Tarjan (edge[i].to); theLOW[X] =min (low[x],low[edge[i].to]); +         } -         Else if(Isin[edge[i].to]) low[x] =min (low[x],dfn[edge[i].to]); $     } $     if(Low[x] = =Dfn[x]) { -Scc++; -          while(S.top ()! =x) { theIsin[s.top ()] =0; -Belong[s.top ()] =SCC;Wuyi S.pop (); thecnt[scc]++; -         } WuISIN[X] =0; BELONG[X] = SCC; S.pop (); cnt[scc]++; -     } About } $ intMain () { -n = read (); m =read (); -Rep (I,1, m) x = Read (), y =read (), Addedge (x, y); -CLR (DFN,0); CLR (CNT,0); ARep (I,1, N)if(!Dfn[i]) Tarjan (i); +CLR (Oud,0); theRep (now,1, N) Travel (now)if(Belong[now]! = belong[edge[i].to]) Oud[belong[now]] =1; -Ans =0; $Rep (I,1, SCC)if(!Oud[i]) { the         if(ANS) {ans =0; Break;} theAns =Cnt[i]; the     } theprintf"%d\n", ans); -     return 0; in}

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BZOJ1051 [HAOI2006] Popular Cattle