cses graphs

cses/graph-algorithms/monsters.cc

@@ -0,0 +1,178 @@
+#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
+//  }}}
+
+static map<char, pair<i32, i32>> dirs{
+    {'R', {0, 1}}, {'L', {0, -1}}, {'D', {1, 0}}, {'U', {-1, 0}}};
+
+void solve() {
+  u32 n, m;
+  cin >> n >> m;
+
+  vec<string> graph(n);
+  for (auto& e : graph)
+    cin >> e;
+
+  queue<pair<i32, i32>> mq, aq;
+
+  u32 sr, sc;
+  for (u32 r = 0; r < n; ++r) {
+    for (u32 c = 0; c < m; ++c) {
+      if (graph[r][c] == 'M') {
+        mq.emplace(r, c);
+        graph[r][c] = '#';
+      } else if (graph[r][c] == 'A') {
+        sr = r, sc = c;
+        aq.emplace(r, c);
+      }
+    }
+  }
+
+  auto valid = [&n, &m](i32 r, i32 c) -> bool {
+    return min(r, c) >= 0 && r < n && c < m;
+  };
+
+  vec<string> trace(n, string(m, ' '));
+  auto print_trace = [&](i32 r, i32 c) -> void {
+    vec<char> path;
+
+    while (r != sr || c != sc) {
+      path.push_back(trace[r][c]);
+      auto dir = dirs.at(trace[r][c]);
+      r -= dir.first;
+      c -= dir.second;
+    }
+
+    reverse(all(path));
+    cout << "YES\n" << path.size() << '\n';
+    for (auto e : path)
+      cout << e;
+  };
+
+  while (!aq.empty()) {
+    u32 mcount = mq.size();
+    for (u32 i = 0; i < mcount; ++i) {
+      auto [r, c] = mq.front();
+      mq.pop();
+
+      for (auto& [_, dir] : dirs) {
+        auto nr = r + dir.first, nc = c + dir.second;
+
+        if (!valid(nr, nc) || graph[nr][nc] == '#') {
+          continue;
+        }
+
+        graph[nr][nc] = '#';
+        mq.emplace(nr, nc);
+      }
+    }
+
+    u32 acount = aq.size();
+    for (u32 i = 0; i < acount; ++i) {
+      auto [r, c] = aq.front();
+      aq.pop();
+
+      if (r == 0 || r == n - 1 || c == 0 || c == m - 1) {
+        print_trace(r, c);
+        return;
+      }
+
+      for (auto& [letter, dir] : dirs) {
+        auto nr = r + dir.first, nc = c + dir.second;
+
+        if (!valid(nr, nc) || trace[nr][nc] != ' ' || graph[nr][nc] == '#') {
+          continue;
+        }
+
+        trace[nr][nc] = letter;
+        aq.emplace(nr, nc);
+      }
+    }
+  }
+
+  NO();
+}
+
+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;
+}
+// }}}