adding mvc here until kactl approves PR

library/graphs/min_vertex_cover.hpp

@@ -0,0 +1,13 @@
+#include "../../kactl/content/graph/HopcroftKarp.h"
+pair<vi, vi> cover(const vector<vi>& g, vi& r) {
+  int n = sz(g), t = 0;
+  vi cl(n), cr(sz(r)), q(n);
+  for (int u : r)
+    if (u != -1) cl[u] = 1;
+  rep(i, 0, n) if (!cl[i]) q[t++] = i;
+  rep(i, 0, t) for (int v : g[q[i]]) {
+    cr[v] = 1;
+    if (r[v] != -1 && cl[r[v]]) cl[q[t++] = r[v]] = 0;
+  }
+  return {cl, cr};
+}

tests/library_checker_aizu_tests/graphs/hopcroft_karp_aizu.test.cpp

@@ -1,7 +1,7 @@
 #define PROBLEM \
   "https://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=GRL_7_A"
 #include "../template.hpp"
-#include "../../../library/graphs/hopcroft_karp.hpp"
+#include "../../../library/graphs/min_vertex_cover.hpp"
 int main() {
   cin.tie(0)->sync_with_stdio(0);
   int l, r, m;
@@ -14,34 +14,18 @@ int main() {
     adj[u].push_back(v);
     edges.emplace_back(u, v);
   }
-  hopcroft_karp res(adj, r);
-  cout << res.m_sz << '\n';
-  // asserting correctness of both to_r, and to_l
-  int size_l = 0;
-  for (int i = 0; i < l; i++) {
-    if (res.to_r[i] != -1) {
-      size_l++;
-      int node_r = res.to_r[i];
-      assert(res.to_l[node_r] == i);
-    }
-  }
+  vi ri(r, -1);
+  int size_matching = hopcroftKarp(adj, ri);
+  auto [mvc_l, mvc_r] = cover(adj, ri);
   int size_r = 0;
-  for (int i = 0; i < r; i++) {
-    if (res.to_l[i] != -1) {
-      size_r++;
-      int node_l = res.to_l[i];
-      assert(res.to_r[node_l] == i);
-    }
-  }
-  assert(size_l == res.m_sz);
-  assert(size_r == res.m_sz);
+  for (int i = 0; i < r; i++)
+    if (ri[i] != -1) size_r++;
+  assert(size_r == size_matching);
   // asserting found min vertex cover is correct
-  int cnt =
-    accumulate(begin(res.mvc_l), end(res.mvc_l), 0) +
-    accumulate(begin(res.mvc_r), end(res.mvc_r), 0);
-  assert(cnt == res.m_sz); // size of min vertex cover
-                           // == size of max matching
-  for (auto [u, v] : edges)
-    assert(res.mvc_l[u] || res.mvc_r[v]);
+  int cnt = accumulate(begin(mvc_l), end(mvc_l), 0) +
+            accumulate(begin(mvc_r), end(mvc_r), 0);
+  assert(cnt == size_matching);
+  for (auto [u, v] : edges) assert(mvc_l[u] || mvc_r[v]);
+  cout << size_matching << '\n';
   return 0;
 }

tests/library_checker_aizu_tests/graphs/hopcroft_karp_lib_checker.test.cpp

@@ -1,7 +1,7 @@
 #define PROBLEM \
   "https://judge.yosupo.jp/problem/bipartitematching"
 #include "../template.hpp"
-#include "../../../library/graphs/hopcroft_karp.hpp"
+#include "../../../library/graphs/min_vertex_cover.hpp"
 int main() {
   cin.tie(0)->sync_with_stdio(0);
   int l, r, m;
@@ -14,36 +14,21 @@ int main() {
     adj[u].push_back(v);
     edges.emplace_back(u, v);
   }
-  hopcroft_karp res(adj, r);
-  cout << res.m_sz << '\n';
-  // asserting correctness of both to_r, and to_l (as
-  // well as printing answer)
-  int size_l = 0;
-  for (int i = 0; i < l; i++) {
-    if (res.to_r[i] != -1) {
-      size_l++;
-      int node_r = res.to_r[i];
-      cout << i << " " << node_r << '\n';
-      assert(res.to_l[node_r] == i);
-    }
-  }
+  vi ri(r, -1);
+  int m_sz = hopcroftKarp(adj, ri);
+  auto [mvc_l, mvc_r] = cover(adj, ri);
+  cout << m_sz << '\n';
   int size_r = 0;
   for (int i = 0; i < r; i++) {
-    if (res.to_l[i] != -1) {
+    if (ri[i] != -1) {
       size_r++;
-      int node_l = res.to_l[i];
-      assert(res.to_r[node_l] == i);
+      cout << ri[i] << ' ' << i << '\n';
     }
   }
-  assert(size_l == res.m_sz);
-  assert(size_r == res.m_sz);
-  // asserting found min vertex cover is correct
-  int cnt =
-    accumulate(begin(res.mvc_l), end(res.mvc_l), 0) +
-    accumulate(begin(res.mvc_r), end(res.mvc_r), 0);
-  assert(cnt == res.m_sz); // size of min vertex cover
-                           // == size of max matching
-  for (auto [u, v] : edges)
-    assert(res.mvc_l[u] || res.mvc_r[v]);
+  assert(size_r == m_sz);
+  int cnt = accumulate(begin(mvc_l), end(mvc_l), 0) +
+            accumulate(begin(mvc_r), end(mvc_r), 0);
+  assert(cnt == m_sz);
+  for (auto [u, v] : edges) assert(mvc_l[u] || mvc_r[v]);
   return 0;
 }