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codeforces/929/f.cc

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+#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
+//  }}}
+
+bitset<1000000 + 1> seen;
+
+void solve() {
+  seen.reset();
+
+  i32 n, m;
+  cin >> n >> m;
+  vec<vec<u32>> grid(n, vec<u32>(m));
+  for (auto& row : grid)
+    for (auto& cell : row)
+      cin >> cell;
+
+  queue<pair<i32, i32>> q{{{0, 0}}};
+  auto index = [&](i32 r, i32 c) {
+    return r * m + c;
+  };
+
+  seen.set(index(0, 0));
+
+  auto valid = [&](i32 r, i32 c) {
+    return min(r, c) >= 0 && r < n && c < m;
+  };
+
+  i32 time = 0;
+  i32 ans = MAX<i32>;
+  while (!q.empty()) {
+    auto qsize{q.size()};
+
+    for (u32 i = 0; i < qsize; ++i) {
+      auto [r, c] = q.front();
+      q.pop();
+
+      if (c == m - 1) {
+        ans = min(ans, time + min(n - 1 - r, (r + 1) % n));
+        continue;
+      }
+
+      i32 T = time % n;
+
+      if (c < m - 1 && grid[(r + T + 1) % n][c + 1] == 0 &&
+          !seen[index(r, c + 1)]) {
+        q.emplace(r, c + 1);
+        seen.set(index(r, c + 1));
+      }
+
+      if (grid[(r + T + 1) % n][c] == 0 && grid[(r + T + 2) % n][c] == 0 &&
+          !seen[index((r + 1) % n, c)]) {
+        q.emplace((r + 1) % n, c);
+        seen.set(index((r + 1) % n, c));
+      }
+    }
+
+    ++time;
+  }
+
+  println("{}", ans == MAX<i32> ? -1 : ans);
+}
+
+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;
+}
+// }}}