強連結成分分解 (From AOJ: GRL_3-C Discussion Solution Statistics Submit Connected Components - Strongly Connected Components)

GRL_3-C.cpp

// AC (http://judge.u-aizu.ac.jp/onlinejudge/review.jsp?rid=1867905#1)
#include<iostream>
#include<string>
#include<vector>
#include<queue>
#include<stack>
#include<map>
#include<set>
#include<algorithm>
#include<functional>
#include<cstdio>
#include<cstdlib>
#include<cmath>
#include<cassert>
using namespace std;

#define mind(a,b) (a>b?b:a)
#define maxd(a,b) (a>b?a:b)
#define absd(x) (x<0?-(x):x)
#define pow2(x) ((x)*(x))
#define rep(i,n) for(int i=0; i<n; ++i)
#define repr(i,n) for(int i=n-1; i>=0; --i)
#define repl(i,s,n) for(int i=s; i<=n; ++i)
#define replr(i,s,n) for(int i=n; i>=s; --i)
#define repf(i,s,n,j) for(int i=s; i<=n; i+=j)
#define repe(e,obj) for(auto e : obj)

#define SP << " " <<
#define COL << " : " <<
#define COM << ", " <<
#define ARR << " -> " <<
#define PNT(STR) cout << STR << endl
#define POS(X,Y) "(" << X << ", " << Y << ")"
#define DEB(A) " (" << #A << ") " << A
#define DEBREP(i,n,val) for(int i=0; i<n; ++i) cout << val << " "; cout << endl
#define ALL(V) (V).begin(), (V).end()
#define INF 1000000007
#define INFLL 10000000000000000007LL
#define EPS 1e-9

typedef unsigned int uint;
typedef unsigned long ulong;
typedef unsigned long long ull;
typedef long long ll;
typedef long double ld;
typedef pair<int, int> P;
//typedef pair<ll, ll> P;
typedef pair<P, int> PI;
typedef pair<int, P> IP;
typedef pair<P, P> PP;
typedef priority_queue<P, vector<P>, greater<P> > pvqueue;

#define V 10003
#define E 30003
int v;
vector<int> g[V];
vector<int> rg[V];
vector<int> ord;

bool used[V];
int group[V];
// 1回目のDFS
// 辺を使って探索し、戻り順に(探索順の)番号をつけていく
void dfs(int s) {
  used[s] = true;
  rep(i, g[s].size()) {
    int t = g[s][i];
    if(!used[t]) {
      dfs(t);
    }
  }
  ord.push_back(s);
}

// 2回目のDFS
// 逆辺を辿ってたどり着ける頂点には同じ番号をつける
void rdfs(int s, int col) {
  group[s] = col;
  used[s] = true;
  rep(i, rg[s].size()) {
    int t = rg[s][i];
    if(!used[t]) {
      rdfs(t, col);
    }
  }
}

// 強連結成分分解
int strongly_connected_components() {
  rep(i, v) used[i] = false;
  rep(i, v) {
    if(!used[i]) dfs(i);
  }
  rep(i, v) used[i] = false;
  assert(ord.size() == v);
  int cnt = 0;
  // 2回目のDFSは番号の逆順に行う
  repr(i, v) {
    int s = ord[i];
    if(!used[s]) rdfs(s, cnt++);
  }
  return cnt;
}

int main() {
  int e;
  cin >> v >> e;
  rep(i, e) {
    int s, t;
    cin >> s >> t;
    g[s].push_back(t);
    rg[t].push_back(s);
  }
  strongly_connected_components();
  int q;
  cin >> q;
  rep(_, q) {
    int u, v;
    cin >> u >> v;
    cout << (group[u] == group[v] ? 1 : 0) << endl;
  }
  return 0;
}