tests/Bipartite_Matching_HopcroftKarp.test.cpp

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Last update: 2025-11-28 10:18:48+07:00
Problem: https://judge.yosupo.jp/problem/bipartitematching

Depends on

Code

#define PROBLEM "https://judge.yosupo.jp/problem/bipartitematching"

#include "../misc/macros.h"
#include "../graph/HopcroftKarp.h"

void solve() {
  int l, r, m;
  cin >> l >> r >> m;
  HopcroftKarp g(l, r);
  for (int i = 0; i < m; ++i) {
    int a, b;
    cin >> a >> b;
    g.add(a, b);
  }
  cout << g.solve() << '\n';
  for (int i = 0; i < r; ++i) {
    if (g.btoa[i] != -1) {
      cout << g.btoa[i] << ' ' << i << '\n';
    }
  }
}

int main() {
  cin.tie(0)->sync_with_stdio(0);
  cin.exceptions(cin.failbit);
  int tc = 1;
  //   cin >> tc;
  for (int i = 1; i <= tc; ++i) {
    solve();
  }
}

#line 1 "tests/Bipartite_Matching_HopcroftKarp.test.cpp"
#define PROBLEM "https://judge.yosupo.jp/problem/bipartitematching"

#line 1 "misc/macros.h"
// #pragma GCC optimize("Ofast,unroll-loops")       // unroll long, simple loops
// #pragma GCC target("avx2,fma")                   // vectorizing code
// #pragma GCC target("lzcnt,popcnt,abm,bmi,bmi2")  // for fast bitset operation

#include <bits/extc++.h>
#include <tr2/dynamic_bitset>

using namespace std;
using namespace __gnu_pbds;  // ordered_set, gp_hash_table
// using namespace __gnu_cxx; // rope

// for templates to work
#define all(x) (x).begin(), (x).end()
#define sz(x) (int) (x).size()
#define pb push_back
#define eb emplace_back
using i32 = int32_t;
using u32 = uint32_t;
using i64 = int64_t;
using u64 = uint64_t;
using i128 = __int128_t;
using u128 = __uint128_t;
using ld = long double;
using pii = pair<i32, i32>;
using vi = vector<i32>;

// fast map
const int RANDOM = chrono::high_resolution_clock::now().time_since_epoch().count();
struct chash {  // customize hash function for gp_hash_table
  int operator()(int x) const { return x ^ RANDOM; }
};
gp_hash_table<int, int, chash> table;

/* ordered set
    find_by_order(k): returns an iterator to the k-th element (0-based)
    order_of_key(k): returns the number of elements in the set that are strictly less than k
*/
template <class T>
using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;

/*  rope
    rope <int> cur = v.substr(l, r - l + 1);
    v.erase(l, r - l + 1);
    v.insert(v.mutable_begin(), cur);
*/
#line 1 "graph/HopcroftKarp.h"
struct HopcroftKarp {
  vector<vi> g; vi btoa, A, B;
  HopcroftKarp(int L, int R) : g(L), btoa(R, -1), A(L), B(R) {}
  void add(int u, int v) { g[u].pb(v); }
  bool dfs(int a, int L) {
    if (A[a] != L) return 0;
    A[a] = -1;
    for (int b : g[a]) if (B[b] == L + 1) {
      B[b] = 0;
      if (btoa[b] == -1 || dfs(btoa[b], L + 1)) return btoa[b] = a, 1;
    }
    return 0;
  }
  int solve() {
    int res = 0; vi cur, next;
    for (;;) {
      fill(all(A), 0), fill(all(B), 0), cur.clear();
      for (int a : btoa) if (a != -1) A[a] = -1;
      for (int a = 0; a < sz(g); ++a) if (!A[a]) cur.pb(a);
      for (int lay = 1;; lay++) {
        bool islast = 0; next.clear();
        for (int a : cur) for (int b : g[a]) {
          if (btoa[b] == -1) B[b] = lay, islast = 1;
          else if (btoa[b] != a && !B[b]) B[b] = lay, next.pb(btoa[b]);
        }
        if (islast) break;
        if (next.empty()) return res;
        for (int a : next) A[a] = lay;
        cur.swap(next);
      }
      for (int a = 0; a < sz(g); ++a) res += dfs(a, 0);
    }
  }
};
#line 5 "tests/Bipartite_Matching_HopcroftKarp.test.cpp"

void solve() {
  int l, r, m;
  cin >> l >> r >> m;
  HopcroftKarp g(l, r);
  for (int i = 0; i < m; ++i) {
    int a, b;
    cin >> a >> b;
    g.add(a, b);
  }
  cout << g.solve() << '\n';
  for (int i = 0; i < r; ++i) {
    if (g.btoa[i] != -1) {
      cout << g.btoa[i] << ' ' << i << '\n';
    }
  }
}

int main() {
  cin.tie(0)->sync_with_stdio(0);
  cin.exceptions(cin.failbit);
  int tc = 1;
  //   cin >> tc;
  for (int i = 1; i <= tc; ++i) {
    solve();
  }
}