finished AMONGUS2, working on laneswitch

codechef/AMONGUS2/AMONGUS2.cpp

@@ -0,0 +1,95 @@
+// https://www.codechef.com/INOIPRAC/problems/AMONGUS2
+
+#include <bits/stdc++.h>
+using namespace std;
+
+#define MAX_N 500000
+
+// "red" is true, "black" is false
+vector<bool> colors(MAX_N);
+vector<bool> vis(MAX_N, false);
+vector<vector<pair<int, int>>> adj(MAX_N);
+
+int numRed, numBlack;
+bool valid;
+
+void dfs(int v)
+{
+  vis[v] = true;
+
+  if (colors[v])
+    ++numRed;
+  else
+    ++numBlack;
+
+  for (int i = 0; i < adj[v].size(); ++i)
+  {
+    const int &w = adj[v][i].first;
+    const int &type = adj[v][i].second;
+
+    bool newColor;
+    if (type == 1) // v accuses w of being a parasite
+      newColor = !colors[v];
+    else // v vouches that w is a human
+      newColor = colors[v];
+
+    if (vis[w])
+    {
+      // validate (check if answer is -1)
+      if (colors[w] != newColor)
+        valid = false;
+    }
+    else
+    {
+      colors[w] = newColor;
+      dfs(w);
+    }
+  }
+}
+
+int main()
+{
+  int T;
+  cin >> T;
+
+  for (int t = 0; t < T; ++t)
+  {
+    int N, Q;
+    cin >> N >> Q;
+
+    fill(vis.begin(), vis.end(), false);
+    for (int i = 0; i < N; ++i)
+      adj[i].clear();
+
+    int type, a, b;
+    for (int i = 0; i < Q; ++i)
+    {
+      cin >> type >> a >> b;
+      --a, --b;
+      adj[a].push_back({b, type});
+      adj[b].push_back({a, type});
+    }
+
+    int ans = 0;
+    for (int i = 0; i < N; ++i)
+      if (!vis[i])
+      {
+        colors[i] = true;
+        numRed = 0, numBlack = 0;
+        valid = true;
+        dfs(i);
+
+        if (!valid)
+        {
+          ans = -1;
+          break;
+        }
+
+        ans += max(numRed, numBlack);
+      }
+
+    cout << ans << '\n';
+  }
+
+  return 0;
+}

codeforces/problems/concomp/concomp.cpp

@@ -0,0 +1,72 @@
+// https://codeforces.com/problemset/problem/920/E
+
+#include <bits/stdc++.h>
+using namespace std;
+
+#define MAX_N 200000
+
+vector<set<int>> reverseAdj(MAX_N);
+vector<int> numInComp(MAX_N, 0);
+set<int> unvisited;
+
+int currComp = 0;
+
+inline bool connected(int v, int w)
+{
+  // it's connected if it's not not connected
+  return reverseAdj[v].find(w) == reverseAdj[v].end();
+}
+
+void dfs(int v)
+{
+  unvisited.erase(v);
+  //cout << v << " is in " << currComp << '\n';
+  ++numInComp[currComp];
+
+  auto curr = unvisited.begin();
+  while (curr != unvisited.end())
+  {
+    int w = *curr;
+    if (!connected(v, w))
+    {
+      ++curr;
+      continue;
+    }
+
+    dfs(w);
+    curr = unvisited.upper_bound(w);
+  }
+}
+
+int main()
+{
+  int n, m;
+  cin >> n >> m;
+
+  int a, b;
+  for (int i = 0; i < m; ++i)
+  {
+    cin >> a >> b;
+    --a, --b;
+    reverseAdj[a].insert(b);
+    reverseAdj[b].insert(a);
+  }
+
+  for (int i = 0; i < n; ++i)
+    unvisited.insert(i);
+
+  while (!unvisited.empty())
+  {
+    dfs(*unvisited.begin());
+    ++currComp;
+  }
+
+  sort(numInComp.begin(), numInComp.begin() + currComp);
+
+  cout << currComp << '\n';
+  for (int i = 0; i < currComp; ++i)
+    cout << numInComp[i] << ' ';
+  cout << '\n';
+
+  return 0;
+}

other/laneswitch/laneswitch.cpp

@@ -0,0 +1,14 @@
+// https://open.kattis.com/contests/acpc17open/problems/laneswitching
+
+#include <bits/stdc++.h>
+using namespace std;
+
+// TODO
+
+int main()
+{
+  int N, M, R;
+  cin >> N >> M >> R;
+
+  return 0;
+}