POJ 1904 King's Quest

#include<cstdio>
#include<cstring>
#include<cmath>
#include<vector>
#include<algorithm>
using namespace std;

const int maxn=5000;
vector<int>G[maxn];
vector<int>FG[maxn];
vector<int>Edge[maxn];
int flag[maxn],dfn[maxn],Belong[maxn];
int N,t,to,Time,Block;
struct Point
{
int id, dfn;
} point[maxn];

bool cmp(const Point&a, const Point&b)
{
return a.dfn>b.dfn;
}

void init()
{
for(int i=0; i<maxn; i++) G[i].clear();
for(int i=0; i<maxn; i++) FG[i].clear();
for(int i=0; i<maxn; i++) Edge[i].clear();

memset(flag,0,sizeof(flag));
memset(dfn,0,sizeof(dfn));
memset(Belong,0,sizeof(Belong));
Time=0,Block=0;
}

void dfs(int now)
{
flag[now]=1;
for(int i=0; i<G[now].size(); i++)
if(!flag[G[now][i]])
dfs(G[now][i]);
Time++;
dfn[now]=Time;
}

void Dfs(int now)
{
Belong[now] = Block;
for (int i = 0; i<FG[now].size(); i++)
if (!Belong[FG[now][i]])
Dfs(FG[now][i]);
}

int main()
{
while(~scanf("%d",&N))
{
init();
for(int i=1; i<=N; i++)
{
scanf("%d",&t);
while(t--)
{
scanf("%d",&to);
G[i].push_back(to+N);
FG[to+N].push_back(i);
Edge[i].push_back(to);
}
}
for(int i=1; i<=N; i++)
{
scanf("%d",&t);
G[t+N].push_back(i);
FG[i].push_back(t+N);
}
for (int i=1; i<=2*N; i++) if(!dfn[i]) dfs(i);
for (int i=0; i<2*N; i++) point[i].id =i+1,point[i].dfn=dfn[i+1];
sort(point, point + N, cmp);
for (int i = 0; i<2*N; i++)
if (!Belong[point[i].id])
Block++, Dfs(point[i].id);
int TOT;
int Cun[maxn];
for(int i=1; i<=N; i++)
{
TOT=0;
sort(Edge[i].begin(),Edge[i].end());
for(int j=0; j<Edge[i].size(); j++)
{
if(Belong[i]==Belong[Edge[i][j]+N])
{
Cun[TOT]=Edge[i][j];
TOT++;
}
}
printf("%d",TOT);
for(int x=0; x<TOT; x++) printf(" %d",Cun[x]);
printf("\n");
}
}
return 0;
}