Submission #495711

#	Time	Username	Problem	Language	Result	Execution time	Memory
495711		chenwz	Mecho (IOI09_mecho)	C++11	100 / 100	180 ms	21600 KiB

mecho

#include <bits/stdc++.h>
using namespace std;
const int NN = 2000 + 4, DX[4] = {1, -1, 0, 0}, DY[4] = {0, 0, 1, -1};
#define _for(i, a, b) for (int i = (a); i < (int)(b); ++i)
string G[NN];
int N, S, D[NN][NN];
bool Vis[NN][NN];
struct Point {
  int x, y;
};
bool check(const Point& st, int delay) {
  if (delay * S >= D[st.x][st.y]) return false;
  queue<pair<int, Point> > Q;
  memset(Vis, 0, sizeof(Vis)), Q.push({delay * S, st}), Vis[st.x][st.y] = true;
  while (!Q.empty()) {
    auto p = Q.front();
    Q.pop();
    int d = p.first, x = p.second.x, y = p.second.y;
    if (G[x][y] == 'D') return true;
    _for(i, 0, 4) {
      int nx = x + DX[i], ny = y + DY[i];
      if (nx < 0 || nx >= N || ny < 0 || ny >= N || G[nx][ny] == 'T' ||
          (d + 1) >= D[nx][ny] || Vis[nx][ny])
        continue;
      Q.push({d + 1, {nx, ny}}), Vis[nx][ny] = true;
    }
  }
  return false;
}
int main() {
  ios::sync_with_stdio(false), cin.tie(0);
  cin >> N >> S;
  queue<Point> Q;
  Point Honey, Home;
  memset(D, -1, sizeof(D));
  _for(i, 0, N) {
    cin >> G[i];
    _for(j, 0, N) {
      char& c = G[i][j];
      if (c == 'H') Q.push({i, j}), D[i][j] = 0;
      if (c == 'M') Honey = {i, j}, c = 'G';
      if (c == 'D') Home = {i, j};
    }
  }
  while (!Q.empty()) {
    Point p = Q.front();
    Q.pop();
    _for(i, 0, 4) {
      int nx = p.x + DX[i], ny = p.y + DY[i];
      if (nx < 0 || nx >= N || ny < 0 || ny >= N || G[nx][ny] != 'G' ||
          D[nx][ny] != -1)
        continue;
      D[nx][ny] = D[p.x][p.y] + S, Q.push({nx, ny});
    }
  }
  D[Home.x][Home.y] = N * N * S;
  int L = -1, R = 2 * N * N;
  while (L + 1 < R) {
    int mid = (L + R) / 2;
    (check(Honey, mid) ? L : R) = mid;
  }
  cout << L << endl;
  return 0;
}

Compilation message (stderr)

mecho.cpp: In function 'int main()':
mecho.cpp:56:21: warning: 'Home.Point::x' may be used uninitialized in this function [-Wmaybe-uninitialized]
   56 |   D[Home.x][Home.y] = N * N * S;
      |   ~~~~~~~~~~~~~~~~~~^~~~~~~~~~~
mecho.cpp:56:21: warning: 'Home.Point::y' may be used uninitialized in this function [-Wmaybe-uninitialized]

• Subtask 1: 100 / 100