This documentation is automatically generated by online-judge-tools/verification-helper
#define PROBLEM \
"https://onlinejudge.u-aizu.ac.jp/courses/library/5/GRL/4/GRL_4_A"
// clang-format off
#include "../template/template.cpp"
#include "../graph/graph-template.cpp"
#include "../graph/get-shortest-path.cpp"
#include "../graph/find-directed-graph-cycle.cpp"
// clang-format on
void Main() {
int V = in(), E = in();
UnWeightedGraph G(V);
rep(i, E) {
int s = in(), t = in();
G[s].push_back(t);
}
out(!findDirectedGraphCycle(G).empty());
}
#line 1 "test/find-directed-graph-cycle.test.cpp"
#define PROBLEM \
"https://onlinejudge.u-aizu.ac.jp/courses/library/5/GRL/4/GRL_4_A"
// clang-format off
#line 1 "template/template.cpp"
#include <algorithm>
#include <array>
#include <cassert>
#include <cmath>
#include <complex>
#include <cstdint>
#include <deque>
#include <functional>
#include <iomanip>
#include <iostream>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>
using namespace std;
#ifdef _DEBUG
#define DUMP(x) std::cerr << (#x) << " = " << (x) << "\n"
#else
#define DUMP(x)
#endif
#define REP(i, a, b) for (int i = (int)(a); i < (int)(b); ++i)
#define EREP(i, a, b) for (int i = (int)(a); i <= (int)(b); ++i)
#define RREP(i, a, b) for (int i = (int)(a)-1; i >= (int)(b); --i)
#define rep(i, n) REP(i, 0, n)
#define erep(i, n) EREP(i, 0, n)
#define rrep(i, n) RREP(i, n, 0)
#define ALL(r) (r).begin(), (r).end()
#define pb push_back
#define eb emplace_back
#define fi first
#define se second
template <typename T>
ostream &operator<<(ostream &os, const vector<T> &v) {
os << "{";
rep(i, v.size()) os << v[i] << (i == (int)v.size() - 1 ? "" : ", ");
os << "}";
return os;
}
template <typename T, typename U>
ostream &operator<<(ostream &os, const pair<T, U> &p) {
return (os << "(" << p.first << ", " << p.second << ")");
}
template <typename T, typename U>
ostream &operator<<(ostream &os, const map<T, U> &m) {
bool first = true;
os << "{";
for (const auto &e : m) {
if (!first)
os << ", ";
os << "{" << e.first << ": " << e.second << "}";
first = false;
}
os << "}";
return os;
}
template <typename T>
ostream &operator<<(ostream &os, const set<T> &s) {
os << "{";
bool first = true;
for (const auto &e : s) {
if (!first)
os << ", ";
os << e;
first = false;
}
os << "}";
return os;
}
template <typename T>
ostream &operator<<(ostream &os, const multiset<T> &s) {
os << "{";
bool first = true;
for (const auto &e : s) {
if (!first)
os << ", ";
os << e;
first = false;
}
os << "}";
return os;
}
template <typename T>
T dup(T x, T y) {
return (x + y - 1) / y;
};
template <typename A, size_t N, typename T>
inline void arrayFill(A (&array)[N], const T &val) {
std::fill((T *)array, (T *)(array + N), val);
}
template <class T>
inline bool chmax(T &a, T b) {
if (a < b) {
a = b;
return true;
}
return false;
}
template <class T>
inline bool chmin(T &a, T b) {
if (a > b) {
a = b;
return true;
}
return false;
}
struct in {
const size_t n = 0;
in() = default;
in(size_t n) : n(n){};
template <typename T>
operator T() {
T ret;
cin >> ret;
return ret;
}
template <typename T>
operator vector<T>() {
assert(n != 0);
vector<T> ret(n);
for (T &x : ret) {
T tmp = in();
x = tmp;
}
return ret;
}
template <typename T, typename U>
operator pair<T, U>() {
pair<T, U> ret;
ret.first = in();
ret.second = in();
return ret;
}
};
namespace fiore {
namespace impl {
template <typename T>
inline void out_impl(const T &x, char end_char) {
std::cout << x << end_char;
}
template <typename T>
inline void out_impl(const vector<T> &x, char end_char) {
bool first = true;
for (const auto &e : x) {
if (!first)
std::cout << ' ';
std::cout << e;
first = false;
}
std::cout << end_char;
}
} // namespace impl
} // namespace fiore
template <typename T>
inline void out(const T &x) {
fiore::impl::out_impl(x, '\n');
};
template <typename T, typename U, typename... Args>
inline void out(const T &x, const U &y, const Args &... args) {
fiore::impl::out_impl(x, ' ');
out(y, args...);
}
using ll = int64_t;
using vint = vector<int32_t>;
using vvint = vector<vint>;
using vll = vector<ll>;
using vvll = vector<vll>;
using vstr = vector<string>;
using pint = pair<int32_t, int32_t>;
using vpint = vector<pint>;
using pll = pair<ll, ll>;
using vpll = vector<pll>;
using setint = set<int32_t>;
using qint = queue<int32_t>;
using qpint = queue<pint>;
constexpr std::int32_t INF = 1001001001;
constexpr std::int64_t LINF = 1001001001001001001;
void Main();
signed main() {
std::cin.tie(nullptr);
std::ios_base::sync_with_stdio(false);
std::cout << std::fixed << std::setprecision(15);
Main();
return 0;
}
#line 1 "graph/graph-template.cpp"
template <typename T = int>
struct Edge {
int from, to;
T cost;
int idx;
Edge() = default;
Edge(const int from, const int to, const T cost = 1, const int idx = -1)
: from(from), to(to), cost(cost), idx(idx) {}
};
template <typename T = int>
using Edges = vector<Edge<T>>;
template <typename T>
using WeightedGraph = vector<Edges<T>>;
using UnWeightedGraph = vector<vector<int>>;
template <typename T = int>
struct Graph {
vector<vector<Edge<T>>> g;
int es;
Graph() = default;
explicit Graph(const int n) : g(n), es(0){};
size_t size() const { return g.size(); }
void add_directed_edge(const int from, const int to, const T cost = 1) {
g[from].emplace_back(from, to, cost, es++);
}
void add_edge(const int from, const int to, const T cost = 1) {
g[from].emplace_back(from, to, cost, es);
g[to].emplace_back(to, from, cost, es++);
}
};
#line 1 "graph/get-shortest-path.cpp"
vector<int> getShortestPath(const UnWeightedGraph &g, const int s,
const int t) {
vector<int> dist(g.size(), INF), prev(g.size(), -1);
dist[s] = 0;
queue<int> q;
q.push(s);
while (!q.empty()) {
const int v = q.front();
q.pop();
for (const auto nv : g[v]) {
if (dist[nv] != INF)
continue;
prev[nv] = v;
dist[nv] = dist[v] + 1;
q.push(nv);
}
}
if (dist[t] == INF)
return vector<int>();
vector<int> shortestPath;
for (int v = t;; v = prev[v]) {
shortestPath.push_back(v);
if (v == s)
break;
}
reverse(shortestPath.begin(), shortestPath.end());
return shortestPath;
}
#line 1 "graph/find-directed-graph-cycle.cpp"
vector<int> findDirectedGraphCycle(const UnWeightedGraph &g) {
const int n = g.size();
vector<int> seen(n, 0), depth(n, -1);
int cycle_s = -1, cycle_t = -1;
auto dfs = [&g, &seen, &depth, &cycle_s, &cycle_t](auto &&self,
const int v) {
seen[v] = 1;
int max_depth_nv = -1;
for (const auto nv : g[v]) {
if (seen[nv] == 1) { // 後退辺が存在
if (max_depth_nv == -1 || depth[max_depth_nv] < depth[nv]) {
max_depth_nv = nv;
}
}
}
if (max_depth_nv != -1) {
cycle_s = max_depth_nv;
cycle_t = v;
return true;
}
for (const auto nv : g[v]) {
if (seen[nv] != 0)
continue;
depth[nv] = depth[v] + 1;
if (self(self, nv))
return true;
}
seen[v] = 2;
return false;
};
rep(s, n) {
if (seen[s] != 0)
continue;
depth[s] = 0;
if (dfs(dfs, s)) {
return getShortestPath(g, cycle_s, cycle_t);
}
}
return vint();
}
#line 8 "test/find-directed-graph-cycle.test.cpp"
// clang-format on
void Main() {
int V = in(), E = in();
UnWeightedGraph G(V);
rep(i, E) {
int s = in(), t = in();
G[s].push_back(t);
}
out(!findDirectedGraphCycle(G).empty());
}