Popular Cows---poj2186 (contraction point, strong unicom)

Title Link:http://poj.org/problem?id=2186

Ask how many points meet other n-1 points can reach this point, is a one-way map;

So we can get the graph to be indented, and then find out the number of points contained in the point 0 of the degree is to obtain the answer;

If the degree is more than 0, then the answer is 0;

#include <cstdio>#include<cstdlib>#include<cmath>#include<iostream>#include<algorithm>#include<cstring>#include<vector>#defineN 10010#defineLson r*2#defineRson r*2+1#defineINF 0XFFFFFFFusing namespacestd;intStack[n], top, out[n], time, flag;intNblock, Block[n], dfn[n], low[n], is[n], N, head[n], CNT;structedge{intV, Next;} E[n*N];voidInit () {Nblock= CNT = top = time = Flag =0; memset (Head,-1,sizeof(Head)); memset (Low,0,sizeof(low)); memset (DFN,0,sizeof(DFN)); memset (Block,0,sizeof(Block)); memset (out,0,sizeof(out)); Memset (IS,0,sizeof(IS)); memset (Stack,0,sizeof(Stack));}voidADD (intUintv) {E[CNT].V=v; E[cnt].next=Head[u]; Head[u]=cnt++;}voidTajar (intu) {Dfn[u]=low[u]=++Time ; Is[u]=1; Stack[top++]=u; intv;  for(intI=head[u]; i!=-1; I=E[i].next) {v=e[i].v; if(!Dfn[v])            {Tajar (v); Low[u]=min (Low[u], low[v]); }        Else{Low[u]=min (Low[u], dfn[v]); }    }    if(low[u]==Dfn[u]) {        ++Nblock;  Do{v=stack[--top]; BLOCK[V]=Nblock; } while(u!=v); }}intMain () {intu, V, m;  while(SCANF ("%d%d", &n, &m)! =EOF)        {Init ();  for(intI=0; i<m; i++) {scanf ("%d%d", &u, &v);        ADD (U,V); }         for(intI=1; i<=n; i++)            if(!Low[i])            {Tajar (i); }         for(intI=1; i<=n; i++)        {             for(intJ=head[i]; j!=-1; j=E[j].next) {u=block[i]; v=BLOCK[E[J].V]; if(u!=v) out[u]++; }} Flag=0; intIndex;  for(intI=1; i<=nblock; i++)        {            if(out[i]==0) {flag++; Index=i; }        }        if(flag>1) {printf ("0\n"); Continue; }        intans=0;  for(intI=1; i<=n; i++)        {            if(block[i]==Index) ans++; } printf ("%d\n", ans); }    return 0;}

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Popular Cows---poj2186 (contraction point, strong unicom)