cp-library
競技プログラミング用 C++ ライブラリ
test/topological_sort.test.cpp
test/topological_sort.test.cpp · GitHub で見る
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コード
#define PROBLEM "https://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=GRL_4_A"
#include "graph/topological_sort.hpp"
#include "components/fast_io.hpp"
int main() {
FastInput input;
FastOutput output;
int n = 0, m = 0;
input.read(n), input.read(m);
std::vector<std::vector<int>> graph(n);
for (int i = 0; i < m; ++i) {
int u = 0, v = 0;
input.read(u), input.read(v);
graph[u].push_back(v);
}
output.println(!topological_sort(graph));
}
#line 1 "test/topological_sort.test.cpp"
#define PROBLEM "https://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=GRL_4_A"
#line 1 "graph/topological_sort.hpp"
#line 1 "components/predecessor_set.hpp"
#line 1 "components/xor_select.hpp"
#include <bit>
#include <cassert>
#include <cstdint>
namespace xor_select_detail {
inline unsigned argmin(std::uint64_t word, unsigned key) {
assert(word && key < 64);
if (std::has_single_bit(word)) return std::countr_zero(word);
if ((word >> key) & 1) return key;
unsigned shift = key & 32;
word = std::rotl(word, shift);
auto exchange = [&](unsigned shift, std::uint64_t mask) {
word = ((word & mask) << shift) | ((word & ~mask) >> shift);
};
exchange(key & 16, 0x0000ffff0000ffffULL);
exchange(key & 8, 0x00ff00ff00ff00ffULL);
exchange(key & 4, 0x0f0f0f0f0f0f0f0fULL);
exchange(key & 2, 0x3333333333333333ULL);
exchange(key & 1, 0x5555555555555555ULL);
return std::countr_zero(word) ^ key;
}
}
#line 5 "components/predecessor_set.hpp"
#include <algorithm>
#include <array>
#line 9 "components/predecessor_set.hpp"
#include <cstddef>
#line 11 "components/predecessor_set.hpp"
#include <cstring>
#include <limits>
#include <span>
#include <string_view>
#include <utility>
#include <vector>
#if defined(__x86_64__) && (defined(__GNUC__) || defined(__clang__))
#include <immintrin.h>
#endif
namespace predecessor_set_detail {
inline void pack_scalar(const char *src, std::uint64_t *dst, std::size_t words) {
for (std::size_t i = 0; i < words; ++i) {
std::uint64_t word = 0;
if constexpr (std::endian::native == std::endian::little) {
for (int j = 0; j < 8; ++j) {
std::uint64_t x;
std::memcpy(&x, src + i * 64 + j * 8, 8);
assert((x & 0xfefefefefefefefeULL) == 0x3030303030303030ULL);
word |= ((x & 0x0101010101010101ULL) * 0x0102040810204080ULL >> 56) << (j * 8);
}
} else {
for (int j = 0; j < 64; ++j) {
assert(src[i * 64 + j] == '0' || src[i * 64 + j] == '1');
word |= std::uint64_t(src[i * 64 + j] - '0') << j;
}
}
dst[i] = word;
}
}
#if defined(__x86_64__) && (defined(__GNUC__) || defined(__clang__))
__attribute__((target("avx2"))) inline void pack_avx2(const char *src, std::uint64_t *dst, std::size_t words) {
const auto ones = _mm256_set1_epi8('1');
for (std::size_t i = 0; i < words; ++i) {
auto a = _mm256_loadu_si256(reinterpret_cast<const __m256i *>(src + i * 64));
auto b = _mm256_loadu_si256(reinterpret_cast<const __m256i *>(src + i * 64 + 32));
assert(_mm256_movemask_epi8(_mm256_cmpeq_epi8(_mm256_and_si256(a, _mm256_set1_epi8(-2)), _mm256_set1_epi8('0'))) == -1);
assert(_mm256_movemask_epi8(_mm256_cmpeq_epi8(_mm256_and_si256(b, _mm256_set1_epi8(-2)), _mm256_set1_epi8('0'))) == -1);
auto low = std::uint32_t(_mm256_movemask_epi8(_mm256_cmpeq_epi8(a, ones)));
auto high = std::uint32_t(_mm256_movemask_epi8(_mm256_cmpeq_epi8(b, ones)));
dst[i] = low | (std::uint64_t(high) << 32);
}
}
#endif
inline void pack(const char *src, std::uint64_t *dst, std::size_t words) {
#if defined(__x86_64__) && (defined(__GNUC__) || defined(__clang__))
if (words >= 4 && __builtin_cpu_supports("avx2")) return pack_avx2(src, dst, words);
#endif
pack_scalar(src, dst, words);
}
}
class PredecessorSet {
int n = 0, count = 0, height = 0;
std::array<int, 6> offset{}, length{};
std::array<int, 16> small{};
bool small_valid = false;
std::vector<std::uint64_t> data;
void mask_tail() {
int bits = n;
for (int h = 0; h < height; ++h) {
if (bits & 63) data[offset[h] + length[h] - 1] &= ~std::uint64_t(0) >> (64 - (bits & 63));
bits = length[h];
}
}
void rebuild() {
count = 0;
for (int i = 0; i < length[0]; ++i) count += std::popcount(data[i]);
for (int h = 1; h < height; ++h)
for (int i = 0; i < length[h - 1]; ++i)
if (data[offset[h - 1] + i]) data[offset[h] + (i >> 6)] |= std::uint64_t(1) << (i & 63);
rebuild_small();
}
template <int H, bool Forward> int descend(int p) const {
if constexpr (H == 0) return p;
else {
auto word = data[offset[H - 1] + p];
int bit = Forward ? std::countr_zero(word) : 63 - std::countl_zero(word);
return descend<H - 1, Forward>(p * 64 + bit);
}
}
template <int H, bool Forward> int ascend(int p) const {
if constexpr (H == 6) return Forward ? n : -1;
else {
if (H >= height) return Forward ? n : -1;
auto word = data[offset[H] + (p >> 6)];
auto mask = Forward ? (~std::uint64_t(1) << (p & 63)) : ~(~std::uint64_t(0) << (p & 63));
word &= mask;
if (word) {
int bit = Forward ? std::countr_zero(word) : 63 - std::countl_zero(word);
return descend<H, Forward>((p & ~63) + bit);
}
return ascend<H + 1, Forward>(p >> 6);
}
}
void rebuild_small() {
small_valid = count <= int(small.size());
if (!small_valid) return;
small.fill(n);
for (int i = 0, p = 0; i < count; ++i) {
auto word = data[p >> 6] >> (p & 63);
p = word ? p + std::countr_zero(word) : ascend<1, true>(p >> 6);
small[i] = p++;
}
}
int small_rank(int p) const {
#if defined(__AVX512F__) && defined(__x86_64__)
auto keys = _mm512_loadu_si512(small.data());
return std::popcount(unsigned(_mm512_cmp_epi32_mask(keys, _mm512_set1_epi32(p), _MM_CMPINT_LT)));
#elif defined(__AVX2__) && defined(__x86_64__)
auto key = _mm256_set1_epi32(p);
auto a = _mm256_cmpgt_epi32(key, _mm256_loadu_si256(reinterpret_cast<const __m256i *>(small.data())));
auto b = _mm256_cmpgt_epi32(key, _mm256_loadu_si256(reinterpret_cast<const __m256i *>(small.data() + 8)));
return std::popcount(unsigned(_mm256_movemask_ps(_mm256_castsi256_ps(a)))) + std::popcount(unsigned(_mm256_movemask_ps(_mm256_castsi256_ps(b))));
#else
int result = 0;
for (int x : small) result += x < p;
return result;
#endif
}
public:
int argmin_xor(std::uint32_t x) const {
if (!count) return -1;
std::uint64_t p = std::uint64_t(x) & ((std::uint64_t(1) << (height * 6)) - 1);
for (int h = 0; h < height; ++h, p >>= 6) {
auto index = p >> 6;
if (index >= unsigned(length[h])) continue;
auto word = data[offset[h] + index];
if (!word) continue;
p = index * 64 + xor_select_detail::argmin(word, p & 63);
while (h--) p = p * 64 + xor_select_detail::argmin(data[offset[h] + p], (x >> (h * 6)) & 63);
return int(p);
}
return -1;
}
int argmax_xor(std::uint32_t x) const { return argmin_xor(~x); }
explicit PredecessorSet(int n = 0, bool filled = false) { assign(n, filled); }
explicit PredecessorSet(std::string_view bits) { assign(bits); }
PredecessorSet(int n, std::span<const std::uint64_t> words) { assign(n, words); }
PredecessorSet(const PredecessorSet &) = default;
PredecessorSet &operator=(const PredecessorSet &) = default;
PredecessorSet(PredecessorSet &&other) noexcept : PredecessorSet() { swap(other); }
PredecessorSet &operator=(PredecessorSet &&other) noexcept {
if (this != &other) { PredecessorSet moved(std::move(other)); swap(moved); }
return *this;
}
void assign(int length, bool filled = false) {
assert(length >= 0);
n = length; count = filled ? n : 0; height = 0;
offset.fill(0); this->length.fill(0);
int total = 0;
for (std::size_t bits = n; bits;) {
std::size_t words = (bits + 63) / 64;
offset[height] = total; this->length[height++] = words;
total += words;
if (words == 1) break;
bits = words;
}
data.assign(total, filled ? ~std::uint64_t(0) : 0);
if (filled) mask_tail();
rebuild_small();
}
void assign(std::string_view bits) {
assert(bits.size() <= std::size_t(std::numeric_limits<int>::max()));
PredecessorSet next(static_cast<int>(bits.size()));
std::size_t words = bits.size() / 64;
predecessor_set_detail::pack(bits.data(), next.data.data(), words);
for (std::size_t i = words * 64; i < bits.size(); ++i) {
assert(bits[i] == '0' || bits[i] == '1');
next.data[i >> 6] |= std::uint64_t(bits[i] - '0') << (i & 63);
}
next.rebuild(); swap(next);
}
void assign(int n, std::span<const std::uint64_t> words) {
assert(n >= 0 && words.size() == (std::size_t(n) + 63) / 64);
PredecessorSet next(n);
std::copy(words.begin(), words.end(), next.data.begin());
if (n & 63) next.data[next.length[0] - 1] &= ~std::uint64_t(0) >> (64 - (n & 63));
next.rebuild(); swap(next);
}
int universe_size() const { return n; }
int size() const { return count; }
bool empty() const { return count == 0; }
bool contains(int p) const { assert(0 <= p && p < n); return data[p >> 6] >> (p & 63) & 1; }
bool insert(int p) {
assert(0 <= p && p < n);
int index = p >> 6;
auto &leaf = data[index];
auto mask = std::uint64_t(1) << (p & 63), before = leaf;
leaf = before | mask;
bool changed = !(before & mask);
count += changed;
if (!before) for (int h = 1; h < height; ++h) {
auto &word = data[offset[h] + (index >> 6)];
auto old = word;
word |= std::uint64_t(1) << (index & 63);
if (old) break;
index >>= 6;
}
small_valid = false;
return changed;
}
bool erase(int p) {
assert(0 <= p && p < n);
int index = p >> 6;
auto &leaf = data[index];
auto mask = std::uint64_t(1) << (p & 63), before = leaf;
leaf = before & ~mask;
bool changed = (before & mask) != 0;
count -= changed;
if (before && !leaf) for (int h = 1; h < height; ++h) {
auto &word = data[offset[h] + (index >> 6)];
word &= ~(std::uint64_t(1) << (index & 63));
if (word) break;
index >>= 6;
}
small_valid = false;
return changed;
}
int next(int p) const {
p = std::max(p, 0);
if (p >= n || !count) return n;
if (small_valid) {
int index = small_rank(p);
return index == count ? n : small[index];
}
auto local = data[p >> 6] >> (p & 63);
if (local) return p + std::countr_zero(local);
return ascend<1, true>(p >> 6);
}
int prev(int p) const {
p = std::min(p, n - 1);
if (p < 0 || !count) return -1;
if (small_valid) {
int index = small_rank(p + 1);
return index ? small[index - 1] : -1;
}
auto local = data[p >> 6] << (63 - (p & 63));
if (local) return p - std::countl_zero(local);
return ascend<1, false>(p >> 6);
}
bool set(int p, bool present) {
assert(0 <= p && p < n);
int index = p >> 6;
auto &leaf = data[index];
auto mask = std::uint64_t(1) << (p & 63), before = leaf;
auto fill = std::uint64_t(0) - present;
leaf = before ^ ((before ^ fill) & mask);
bool old = (before & mask) != 0;
count += int(present) - int(old);
if ((!before) != (!leaf)) for (int h = 1; h < height; ++h) {
auto &word = data[offset[h] + (index >> 6)];
auto previous = word;
word = previous ^ ((previous ^ fill) & (std::uint64_t(1) << (index & 63)));
if ((!previous) == (!word)) break;
index >>= 6;
}
small_valid = false;
return old != present;
}
int min() const { return next(0); }
int max() const { return prev(n - 1); }
void clear() { std::fill(data.begin(), data.end(), 0); count = 0; small_valid = false; }
void fill() {
std::fill(data.begin(), data.end(), ~std::uint64_t(0));
mask_tail();
count = n;
rebuild_small();
}
template <class F> void for_each(int l, int r, F &&f) const {
assert(0 <= l && l <= r && r <= n);
for (int p = next(l); p < r;) {
int base = p & ~63;
auto word = data[p >> 6] & (~std::uint64_t(0) << (p & 63));
if (r - base < 64) word &= ~std::uint64_t(0) >> (64 - (r - base));
while (word) { f(base + std::countr_zero(word)); word &= word - 1; }
if (r - base <= 64) break;
p = next(base + 64);
}
}
template <class F> void for_each(F &&f) const { for_each(0, n, f); }
std::vector<int> to_vector() const {
std::vector<int> out; out.reserve(count);
for_each([&](int x) { out.push_back(x); }); return out;
}
std::span<const std::uint64_t> words() const & { return {data.data(), std::size_t(length[0])}; }
void words() const && = delete;
void swap(PredecessorSet &other) noexcept {
using std::swap;
swap(n, other.n); swap(count, other.count); swap(height, other.height);
offset.swap(other.offset); length.swap(other.length); data.swap(other.data); small.swap(other.small); swap(small_valid, other.small_valid);
}
std::size_t memory_usage() const { return data.capacity() * sizeof(std::uint64_t); }
};
#line 8 "graph/topological_sort.hpp"
#include <functional>
#line 10 "graph/topological_sort.hpp"
#include <optional>
#line 12 "graph/topological_sort.hpp"
template<bool Lexicographical = false, class G>
std::optional<std::vector<int>> topological_sort(const G &graph) {
assert(graph.size() <= std::size_t(std::numeric_limits<int>::max()));
int n = static_cast<int>(graph.size());
std::vector<std::size_t> indegree(n);
for (int v = 0; v < n; ++v) for (int to : graph[v]) {
assert(0 <= to && to < n);
++indegree[to];
}
std::vector<int> order;
order.reserve(n);
if constexpr (Lexicographical) {
std::vector<int> ready;
for (int v = 0; v < n; ++v) if (!indegree[v]) ready.push_back(v);
std::optional<PredecessorSet> ready_set;
bool use_set = ready.size() > 128;
if (use_set) {
ready_set.emplace(n);
for (int v : ready) ready_set->insert(v);
ready.clear();
} else std::make_heap(ready.begin(), ready.end(), std::greater<int>{});
while (use_set || !ready.empty()) {
int v;
if (use_set) {
v = ready_set->min();
ready_set->erase(v);
} else {
std::pop_heap(ready.begin(), ready.end(), std::greater<int>{});
v = ready.back();
ready.pop_back();
}
order.push_back(v);
for (int to : graph[v]) if (--indegree[to] == 0) {
if (use_set) ready_set->insert(to);
else {
ready.push_back(to);
std::push_heap(ready.begin(), ready.end(), std::greater<int>{});
}
}
if (use_set && ready_set->size() <= 32) {
while (!ready_set->empty()) {
int x = ready_set->min();
ready_set->erase(x);
ready.push_back(x);
}
std::make_heap(ready.begin(), ready.end(), std::greater<int>{});
use_set = false;
} else if (!use_set && ready.size() > 128) {
if (!ready_set) ready_set.emplace(n);
for (int x : ready) ready_set->insert(x);
ready.clear();
use_set = true;
}
}
} else {
for (int v = 0; v < n; ++v) if (!indegree[v]) order.push_back(v);
for (std::size_t head = 0; head < order.size(); ++head)
for (int to : graph[order[head]]) if (--indegree[to] == 0) order.push_back(to);
}
if (order.size() != std::size_t(n)) return std::nullopt;
return order;
}
#line 1 "components/fast_io.hpp"
#line 8 "components/fast_io.hpp"
#include <charconv>
#line 11 "components/fast_io.hpp"
#include <cstdio>
#line 13 "components/fast_io.hpp"
#include <memory>
#include <stdexcept>
#include <string>
#line 17 "components/fast_io.hpp"
#include <type_traits>
#if defined(__unix__) || defined(__APPLE__)
#include <sys/mman.h>
#include <sys/stat.h>
#include <unistd.h>
#endif
namespace fast_io_detail { struct BulkInput; struct BulkOutput; }
class FastInput {
friend struct fast_io_detail::BulkInput;
static constexpr std::size_t capacity = 1 << 16;
FILE *file = nullptr;
std::unique_ptr<char[]> buffer;
const char *current = "", *end = current;
std::string scratch;
void *mapping = nullptr;
std::size_t mapped_size = 0;
bool refill() {
if (!file) return false;
std::size_t n = std::fread(buffer.get(), 1, capacity, file);
current = buffer.get();
end = current + n;
return n;
}
static const char *scan(const char *p, const char *end) {
while (end - p >= 8) {
std::uint64_t x;
std::memcpy(&x, p, 8);
if ((x - 0x2121212121212121ULL) & ~x & 0x8080808080808080ULL) break;
p += 8;
}
while (p != end && static_cast<unsigned char>(*p) > ' ') ++p;
return p;
}
public:
explicit FastInput(FILE *input = stdin) {
#if defined(__unix__) || defined(__APPLE__)
struct stat status;
int fd = fileno(input);
auto offset = ftello(input);
if (fd >= 0 && offset >= 0 && !fstat(fd, &status) && S_ISREG(status.st_mode) && status.st_size > offset) {
mapped_size = status.st_size;
mapping = mmap(nullptr, mapped_size, PROT_READ, MAP_PRIVATE, fd, 0);
if (mapping != MAP_FAILED) {
current = static_cast<const char *>(mapping) + offset;
end = static_cast<const char *>(mapping) + mapped_size;
return;
}
mapping = nullptr;
}
#endif
file = input;
buffer = std::make_unique_for_overwrite<char[]>(capacity);
}
explicit FastInput(std::string_view input) : current(input.empty() ? "" : input.data()), end(current + input.size()) {}
FastInput(const FastInput &) = delete;
FastInput &operator=(const FastInput &) = delete;
~FastInput() {
#if defined(__unix__) || defined(__APPLE__)
if (mapping) munmap(mapping, mapped_size);
#endif
}
std::string_view token() {
while (true) {
while (current != end && static_cast<unsigned char>(*current) <= ' ') ++current;
if (current != end) break;
if (!refill()) return {};
}
const char *begin = current;
current = scan(current, end);
if (current != end || !file) return {begin, std::size_t(current - begin)};
scratch.assign(begin, end);
while (refill()) {
current = scan(current, end);
scratch.append(buffer.get(), std::size_t(current - buffer.get()));
if (current != end) break;
}
return scratch;
}
template <class T>
bool read(T &value) {
if constexpr (std::is_integral_v<T> && !std::is_same_v<T, bool>) {
while (true) {
while (current != end && static_cast<unsigned char>(*current) <= ' ') ++current;
if (current != end) break;
if (!refill()) return false;
}
if constexpr (std::is_unsigned_v<T> && sizeof(T) == 4 && std::endian::native == std::endian::little) {
if (end - current >= 11) {
std::uint64_t x;
std::memcpy(&x, current, 8);
if (!(((x + 0x4646464646464646ULL) | (x - 0x3030303030303030ULL)) & 0x8080808080808080ULL)) {
x &= 0x0f0f0f0f0f0f0f0fULL;
x = (x * 10 + (x >> 8)) & 0x00ff00ff00ff00ffULL;
x = (x * 100 + (x >> 16)) & 0x0000ffff0000ffffULL;
std::uint64_t v = std::uint32_t(x * 10000 + (x >> 32));
int n = 8;
for (; n < 10 && static_cast<unsigned char>(current[n]) - unsigned('0') < 10; ++n)
v = v * 10 + (current[n] - '0');
if (static_cast<unsigned char>(current[n]) <= ' ' && v <= 0xffffffffULL) {
current += n;
value = T(v);
return true;
}
}
}
}
T parsed{};
auto result = std::from_chars(current, end, parsed);
if (result.ec == std::errc{} && (result.ptr != end ? static_cast<unsigned char>(*result.ptr) <= ' ' : !file)) {
current = result.ptr;
value = parsed;
return true;
}
}
auto s = token();
if (s.empty()) return false;
if constexpr (std::is_same_v<T, bool>) {
assert(s == "0" || s == "1");
value = s[0] == '1';
} else if constexpr (std::is_integral_v<T>) {
auto result = std::from_chars(s.data(), s.data() + s.size(), value);
assert(result.ec == std::errc{} && result.ptr == s.data() + s.size());
(void)result;
} else value = T(s);
return true;
}
};
class FastOutput {
friend struct fast_io_detail::BulkOutput;
inline static constexpr auto quads = [] {
std::array<std::array<char, 4>, 10000> table{};
for (int i = 0; i < 10000; ++i)
table[i] = {char('0' + i / 1000), char('0' + i / 100 % 10), char('0' + i / 10 % 10), char('0' + i % 10)};
return table;
}();
FILE *file;
std::unique_ptr<char[]> buffer = std::make_unique_for_overwrite<char[]>(1 << 16);
std::size_t capacity = 1 << 16, length = 0;
char *reserve(std::size_t n) {
if (n > capacity - length) {
if (!flush()) throw std::runtime_error("output failed");
if (n > capacity) {
std::size_t next = std::max(n, 2 * capacity);
buffer = std::make_unique_for_overwrite<char[]>(next);
capacity = next;
}
}
return buffer.get() + length;
}
public:
explicit FastOutput(FILE *output = stdout) : file(output) {}
FastOutput(const FastOutput &) = delete;
FastOutput &operator=(const FastOutput &) = delete;
~FastOutput() { flush(); }
bool flush() {
std::size_t offset = 0;
while (offset < length) {
auto n = std::fwrite(buffer.get() + offset, 1, length - offset, file);
if (!n) {
std::memmove(buffer.get(), buffer.get() + offset, length - offset);
length -= offset;
return false;
}
offset += n;
}
length = 0;
return std::fflush(file) == 0;
}
void write(char c) { *reserve(1) = c; ++length; }
void write(__uint128_t value) {
char digits[40];
char *end = digits + sizeof(digits), *begin = end;
do { *--begin = char('0' + value % 10); value /= 10; } while (value);
write(std::string_view(begin, end - begin));
}
void write(__int128_t value) {
__uint128_t magnitude = __uint128_t(value);
if (value < 0) write('-'), magnitude = 0 - magnitude;
write(magnitude);
}
void write(std::string_view s) {
char *out = reserve(s.size());
if (!s.empty()) std::memcpy(out, s.data(), s.size());
length += s.size();
}
template <class T> requires std::is_integral_v<T>
void write(T value) {
char *out = reserve(32);
if constexpr (std::is_same_v<T, bool>) *out = '0' + value, ++length;
else if constexpr (std::is_unsigned_v<T> && sizeof(T) == 4) {
char *p = out;
if (value >= 100000000) {
auto high = value / 100000000, low = value % 100000000;
p = std::to_chars(p, p + 2, high).ptr;
std::memcpy(p, quads[low / 10000].data(), 4);
std::memcpy(p + 4, quads[low % 10000].data(), 4);
p += 8;
} else if (value >= 10000) {
p = std::to_chars(p, p + 4, value / 10000).ptr;
std::memcpy(p, quads[value % 10000].data(), 4);
p += 4;
} else p = std::to_chars(p, p + 4, value).ptr;
length += p - out;
} else length += std::to_chars(out, out + 32, value).ptr - out;
}
template <class T> requires requires(const T &value, char *out) { value.decimal_capacity(); value.to_chars(out); }
void write(const T &value) {
char *out = reserve(value.decimal_capacity());
length += value.to_chars(out) - out;
}
template <class T>
void println(const T &value) { write(value); write('\n'); }
};
#line 4 "test/topological_sort.test.cpp"
int main() {
FastInput input;
FastOutput output;
int n = 0, m = 0;
input.read(n), input.read(m);
std::vector<std::vector<int>> graph(n);
for (int i = 0; i < m; ++i) {
int u = 0, v = 0;
input.read(u), input.read(v);
graph[u].push_back(v);
}
output.println(!topological_sort(graph));
}