// competitive-verifier: PROBLEM https://judge.yosupo.jp/problem/general_matching/
#include "../../../src/graph/blossom/u/lib.hpp"
using namespace tifa_libs;
int main() {
std::cin.tie(nullptr)->std::ios::sync_with_stdio(false);
u32 n, m;
std::cin >> n >> m;
blossom bl(n);
for (u32 i = 0, u, v; i < m; ++i) {
std::cin >> u >> v;
bl.add_edge(u + 1, v + 1);
}
auto res = bl();
std::cout << res.size() << '\n';
for (auto [u, v] : res) std::cout << u - 1 << ' ' << v - 1 << '\n';
return 0;
}
#line 1 "test/cpv/library-checker-graph/general_matching.cpp"
// competitive-verifier: PROBLEM https://judge.yosupo.jp/problem/general_matching/
#line 2 "src/graph/blossom/u/lib.hpp"
#line 2 "src/util/alias/others/lib.hpp"
#line 2 "src/util/consts/lib.hpp"
#line 2 "src/util/alias/num/lib.hpp"
#line 2 "src/util/util/lib.hpp"
// https://github.com/Tiphereth-A/CP-lib
#include <bits/extc++.h>
// clang-format off
namespace tifa_libs {
#define CEXP constexpr
#define CEXPE constexpr explicit
#define CR const&
#define CP const*
#define PC *const
#define CPC const*const
#define TPN typename
#define NE noexcept
#define CNE const noexcept
#define ND [[nodiscard]]
#define cT_(...) std::conditional_t<sizeof(__VA_ARGS__) <= sizeof(size_t) * 2, __VA_ARGS__, __VA_ARGS__ CR>
// NOLINTNEXTLINE(misc-const-correctness)
#define flt_(T, i, l, r, ...) for (T i = (l), i##e = (r)__VA_OPT__(, ) __VA_ARGS__; i < i##e; ++i)
#define retif_(cond, if_true, ...) if cond return if_true __VA_OPT__(; else return __VA_ARGS__)
#ifdef ONLINE_JUDGE
#undef assert
#define assert(x) 42
#endif
using namespace std::ranges;
using namespace std::literals;
template <class T>
CEXP T abs(T x) NE { retif_((x < 0), -x, x); }
} // namespace tifa_libs
// clang-format on
#line 4 "src/util/alias/num/lib.hpp"
// clang-format off
namespace tifa_libs {
#define mk0_(w, t) using w = t; using c##w = const t
#define mk_(w, t) mk0_(w, t); CEXP w operator""_##w(unsigned long long x) NE { return (w)x; }
mk_(i8, int8_t) mk_(u8, uint8_t) mk_(i16, int16_t) mk_(u16, uint16_t) mk_(i32, int32_t) mk_(u32, uint32_t) mk_(i64, int64_t) mk_(u64, uint64_t) mk_(isz, ssize_t) mk_(usz, size_t) mk_(chr, char) mk_(schr, signed char) mk_(uchr, unsigned char) mk_(sint, signed) mk_(uint, unsigned);
mk0_(i128, __int128_t); mk0_(u128, __uint128_t); mk0_(f32, float); mk0_(f64, double); mk0_(f128, long double);
#undef mk0_
#undef mk_
} // namespace tifa_libs
// clang-format on
#line 4 "src/util/consts/lib.hpp"
// clang-format off
namespace tifa_libs {
using std::numbers::pi_v;
template <std::floating_point FP>
inline FP eps_v = std::sqrt(std::numeric_limits<FP>::epsilon());
template <std::floating_point FP>
CEXP void set_eps(FP v) NE { eps_v<FP> = v; }
CEXP u32 TIME = ((__TIME__[0] & 15) << 20) | ((__TIME__[1] & 15) << 16) | ((__TIME__[3] & 15) << 12) | ((__TIME__[4] & 15) << 8) | ((__TIME__[6] & 15) << 4) | (__TIME__[7] & 15);
CEXP auto STR2U16 = [] { std::array<u32, 65536> table{}; table.fill(-1_u32); flt_ (u32, i, 48, 58) flt_ (u32, j, 48, 58) table[i << 8 | j] = (j & 15) * 10 + (i & 15); return table; }();
inline const auto fn_0 = [](auto&&...) NE {};
inline const auto fn_is0 = [](auto x) NE { return x == 0; };
} // namespace tifa_libs
// clang-format on
#line 4 "src/util/alias/others/lib.hpp"
namespace tifa_libs {
template <class T>
struct chash {
CEXP static u64 C = u64(pi_v<f128> * 2e18) | 71;
CEXP u64 operator()(T x) CNE { return __builtin_bswap64(((u64)x ^ TIME) * C); }
};
// clang-format off
#define mk_(w, t) using w = t; using c##w = const t;
mk_(strn, std::string) mk_(strnv, std::string_view)
#undef mk_
template <class T> struct edge_t { T w; u32 u, v; CEXP auto operator<=>(edge_t CR) const = default; }; template <class T> using cedge_t = const edge_t<T>;
template <class T> struct pt3 { T _0, _1, _2; CEXP auto operator<=>(pt3 CR) const = default; }; template <class T> using cpt3 = const pt3<T>;
template <class T> struct pt4 { T _0, _1, _2, _3; CEXP auto operator<=>(pt4 CR) const = default; }; template <class T> using cpt4 = const pt4<T>;
#define mkT_(w, t, ...) template <class T> using w = t __VA_OPT__(, ) __VA_ARGS__; template <class T> using c##w = const t __VA_OPT__(, ) __VA_ARGS__;
mkT_(ptt, std::pair<T, T>) mkT_(alc, std::pmr::polymorphic_allocator<T>) mkT_(vec, std::vector<T>) mkT_(vvec, vec<vec<T>>) mkT_(v3ec, vvec<vec<T>>) mkT_(vecpt, vec<ptt<T>>) mkT_(vvecpt, vvec<ptt<T>>) mkT_(ptvec, ptt<vec<T>>) mkT_(ptvvec, ptt<vvec<T>>)
#undef mkT_
template <class T> using itl = std ::initializer_list<T>;
template <class T, usz ext = std::dynamic_extent> using spn = std::span<T const, ext>;
template <class T, usz N> using arr = std::array<T, N>; template <class T, usz N> using carr = std::array<const T, N>;
template <class U, class T> using vecp = vec<std::pair<U, T>>; template <class U, class T> using vvecp = vvec<std::pair<U, T>>;
template <class U, class T> using vvecp = vvec<std::pair<U, T>>; template <class U, class T> using vvvecp = vvec<vvec<std::pair<U, T>>>;
#ifdef PB_DS_ASSOC_CNTNR_HPP
template <class T, class C = std::less<T>> using set = __gnu_pbds::tree<T, __gnu_pbds::null_type, C>;
template <class K, class V, class C = std::less<K>> using map = __gnu_pbds::tree<K, V, C>;
// hset<u64> s({}, {}, {}, {}, {1<<16});
template <class T, class HF = chash<T>> using hset = __gnu_pbds::gp_hash_table<T, __gnu_pbds::null_type, HF>;
// hmap<u64, int> s({}, {}, {}, {}, {1<<16});
template <class K, class V, class HF = chash<K>> using hmap = __gnu_pbds::gp_hash_table<K, V, HF>;
#else
using std::set, std::map;
template <class T, class HF = chash<T>> using hset = std::unordered_set<T, HF>;
template <class K, class V, class HF = chash<K>> using hmap = std::unordered_map<K, V, HF>;
#endif
#ifdef PB_DS_PRIORITY_QUEUE_HPP
template <class T, class C = std::less<T>> using pq = __gnu_pbds::priority_queue<T, C>;
#else
template <class T, class C = std::less<T>> using pq = std::priority_queue<T, vec<T>, C>;
#endif
template <class T> using pqg = pq<T, std::greater<T>>;
// clang-format on
#define mk1_(V, A, T) using V##A = V<T>;
#define mk_(V, A, T) mk1_(V, A, T) mk1_(c##V, A, T)
#define mk(A, T) mk_(edge_t, A, T) mk_(ptt, A, T) mk_(pt3, A, T) mk_(pt4, A, T) mk_(vec, A, T) mk_(vvec, A, T) mk_(v3ec, A, T) mk_(vecpt, A, T) mk_(vvecpt, A, T) mk_(ptvec, A, T) mk_(ptvvec, A, T) mk1_(spn, A, T) mk1_(itl, A, T)
mk(b, bool) mk(c, chr) mk(i, i32) mk(u, u32) mk(ii, i64) mk(uu, u64) mk(t, isz) mk(z, usz) mk(f, f32) mk(d, f64) mk(s, strn);
#undef mk
#undef mk_
#undef mk1_
} // namespace tifa_libs
#line 4 "src/graph/blossom/u/lib.hpp"
namespace tifa_libs {
//! 1-indexed, [1, n]
class blossom {
u32 n;
vvecu g;
vecu mate, first;
vecb white;
vecptu label;
public:
CEXPE blossom(u32 n) NE { init(n); }
CEXP void init(u32 n_) NE {
n = n_;
g = vvecu(n + 1);
mate = first = vecu(n + 1);
label = vecptu(n + 1);
white = vecb(n + 1);
}
CEXP void add_edge(u32 u, u32 v) NE { g[u].push_back(v), g[v].push_back(u); }
vecptu operator()() NE {
flt_ (u32, s, 1, n + 1)
if (!mate[s]) augment(s);
flt_ (u32, s, 1, n + 1)
if (!mate[s] && !white[s]) assert(!augment(s));
vecptu ans;
flt_ (u32, s, 1, n + 1)
if (s < mate[s]) ans.emplace_back(s, mate[s]);
return ans;
}
private:
CEXP u32 gf(u32 x) NE { retif_((!white[first[x]]), first[x], first[x] = gf(first[x])); }
CEXP void match(u32 p, u32 b) NE {
if (swap(b, mate[p]); mate[b] != p) return;
if (auto [k, v] = label[p]; !v) mate[b] = k, match(k, b);
else match(k, v), match(v, k);
}
bool augment(u32 s) NE {
assert(s), white[s] = true, first[s] = 0, label[s] = {0, 0};
std::queue<u32> q({s});
while (!q.empty()) {
cu32 a = q.front();
for (q.pop(); auto b : g[a])
if (assert(b); white[b]) {
u32 x = gf(a), y = gf(b), lca = 0;
while (x || y) {
if (y) swap(x, y);
if (label[x] == pttu{a, b}) {
lca = x;
break;
}
label[x] = {a, b}, x = gf(label[mate[x]].first);
}
for (u32 v : {gf(a), gf(b)})
while (v != lca) {
assert(!white[v]);
q.push(v);
white[v] = true, first[v] = lca;
v = gf(label[mate[v]].first);
}
} else if (!mate[b]) {
match(mate[b] = a, b), white = vecb(n + 1);
return true;
} else if (!white[mate[b]]) {
white[mate[b]] = true;
label[first[mate[b]] = b] = {0, 0}, label[mate[b]] = {a, 0};
q.push(mate[b]);
}
}
return false;
}
};
} // namespace tifa_libs
#line 3 "test/cpv/library-checker-graph/general_matching.cpp"
using namespace tifa_libs;
int main() {
std::cin.tie(nullptr)->std::ios::sync_with_stdio(false);
u32 n, m;
std::cin >> n >> m;
blossom bl(n);
for (u32 i = 0, u, v; i < m; ++i) {
std::cin >> u >> v;
bl.add_edge(u + 1, v + 1);
}
auto res = bl();
std::cout << res.size() << '\n';
for (auto [u, v] : res) std::cout << u - 1 << ' ' << v - 1 << '\n';
return 0;
}
test/cpv/library-checker-graph/general_matching.cpp