cses graphs

cses/graph-algorithms/building-teams.cc

@@ -0,0 +1,137 @@
+#include <bits/stdc++.h>  // {{{
+
+#include <version>
+#ifdef __cpp_lib_ranges_enumerate
+#include <ranges>
+namespace rv = std::views;
+namespace rs = std::ranges;
+#endif
+
+// https://codeforces.com/blog/entry/96344
+
+#pragma GCC optimize("O2,unroll-loops")
+#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
+
+using namespace std;
+
+using i32 = int32_t;
+using u32 = uint32_t;
+using i64 = int64_t;
+using u64 = uint64_t;
+using f64 = double;
+using f128 = long double;
+
+#if __cplusplus >= 202002L
+template <typename T>
+constexpr T MIN = std::numeric_limits<T>::min();
+
+template <typename T>
+constexpr T MAX = std::numeric_limits<T>::max();
+
+template <typename T>
+[[nodiscard]] static T sc(auto&& x) {
+  return static_cast<T>(x);
+}
+
+template <typename T>
+[[nodiscard]] static T sz(auto&& x) {
+  return static_cast<T>(x.size());
+}
+#endif
+
+static void NO() {
+  std::cout << "NO\n";
+}
+
+static void YES() {
+  std::cout << "YES\n";
+}
+
+template <typename T>
+using vec = std::vector<T>;
+
+#define all(x) (x).begin(), (x).end()
+#define rall(x) (x).rbegin(), (x).rend()
+#define ff first
+#define ss second
+
+#ifdef LOCAL
+#define db(...) std::print(__VA_ARGS__)
+#define dbln(...) std::println(__VA_ARGS__)
+#else
+#define db(...)
+#define dbln(...)
+#endif
+//  }}}
+
+void solve() {
+  u32 n, m;
+  cin >> n >> m;
+
+  // -1/0/1 -> unset, c0, c1
+  vector<i32> color(n + 1, -1);
+
+  vec<vec<u32>> forest(n + 1);
+
+  for (u32 i = 0; i < m; ++i) {
+    u32 u, v;
+    cin >> u >> v;
+    forest[u].push_back(v);
+    forest[v].push_back(u);
+  }
+
+  auto bfs = [&](u32 u) -> bool {
+    queue<u32> q{{u}};
+    color[u] = 0;
+
+    while (!q.empty()) {
+      u = q.front();
+      q.pop();
+
+      for (auto v : forest[u]) {
+        if (color[v] == color[u]) {
+          return false;
+        }
+        if (color[v] == -1) {
+          color[v] = 1 - color[u];
+          q.push(v);
+        }
+      }
+    }
+
+    return true;
+  };
+
+  for (u32 u = 1; u <= n; ++u) {
+    if (color[u] == -1 && !bfs(u)) {
+      cout << "IMPOSSIBLE\n";
+      return;
+    }
+  }
+
+  for (u32 i = 1; i <= n; ++i) {
+    cout << color[i] + 1 << " \n"[i == n];
+  }
+}
+
+int main() {  // {{{
+  std::cin.exceptions(std::cin.failbit);
+
+#ifdef LOCAL
+  std::cerr.rdbuf(std::cout.rdbuf());
+  std::cout.setf(std::ios::unitbuf);
+  std::cerr.setf(std::ios::unitbuf);
+#else
+  std::cin.tie(nullptr)->sync_with_stdio(false);
+#endif
+
+  u32 tc = 1;
+  // std::cin >> tc;
+
+  for (u32 t = 0; t < tc; ++t) {
+    solve();
+  }
+
+  return 0;
+}
+// }}}