Submission #518468

#	Time	Username	Problem	Language	Result	Execution time	Memory
518468		Alex_tz307	Mecho (IOI09_mecho)	C++17	10 / 100	188 ms	6232 KiB

mecho

#include <bits/stdc++.h>
#define INF 0x3f3f3f3f

using namespace std;

void testCase() {
  int n, s;
  cin >> n >> s;
  vector<string> a(n);
  queue<pair<int, int>> q;
  vector<vector<int>> bee(n, vector<int>(n, INF));
  int istart = -1, jstart = -1, istop = -1, jstop = -1;
  for (int i = 0; i < n; ++i) {
    cin >> a[i];
    for (int j = 0; j < n; ++j) {
      if (a[i][j] == 'H') {
        bee[i][j] = 1;
        q.emplace(i, j);
      } else if (a[i][j] == 'M') {
        istart = i, jstart = j;
      } else if (a[i][j] == 'D') {
        istop = i, jstop = j;
      }
    }
  }
  const int di[] = {-1, 0, 1, 0}, dj[] = {0, 1, 0, -1};
  auto valid = [&](const int &i, const int &j) -> bool {
    return 0 <= min(i, j) && max(i, j) < n && a[i][j] != 'T' && a[i][j] != 'H';
  };
  while (!q.empty()) {
    int i, j;
    tie(i, j) = q.front();
    q.pop();
    for (int k = 0; k < 4; ++k) {
      int iv = i + di[k], jv = j + dj[k];
      if (valid(iv, jv) && a[iv][jv] != 'D' && bee[iv][jv] == INF) {
        bee[iv][jv] = bee[i][j] + 1;
        q.emplace(iv, jv);
      }
    }
  }
  auto checkDistance = [&](const int &m, const int &b) -> bool {
    return m / s < b;
  };
  auto check = [&](const int &t) -> bool {
    vector<vector<int>> dp(n, vector<int>(n, INF));
    queue<pair<int, int>> q;
    dp[istart][jstart] = t;
    q.emplace(istart, jstart);
    while (!q.empty()) {
      int i, j;
      tie(i, j) = q.front();
      q.pop();
      for (int k = 0; k < 4; ++k) {
        int iv = i + di[k], jv = j + dj[k];
        if (valid(iv, jv) && dp[iv][jv] == INF && checkDistance(dp[i][j] + 1, bee[iv][jv] - t)) {
          dp[iv][jv] = dp[i][j] + 1;
          q.emplace(iv, jv);
        }
      }
    }
    if (dp[istop][jstop] == INF) {
      return false;
    }
    return true;
  };
  int l = 0, r = bee[istart][jstart] - 1, ans = -1;
  while (l <= r) {
    int mid = (l + r) / 2;
    if (check(mid)) {
      ans = mid;
      l = mid + 1;
    } else {
      r = mid - 1;
    }
  }
  cout << ans << '\n';
}

int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  int tests = 1;
  for (int tc = 0; tc < tests; ++tc) {
    testCase();
  }
  return 0;
}

• Subtask 1: 10 / 100