Submission #495680

#	Time	Username	Problem	Language	Result	Execution time	Memory
495680		chenwz	Mecho (IOI09_mecho)	C++14	100 / 100	229 ms	22436 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)
char G[NN][NN];
int N, S, B[NN][NN];
bool Vis[NN][NN];
struct Point {
  int x, y;
};
bool check(const Point& st, int delay) {
  if (delay * S >= B[st.x][st.y]) return false;
  memset(Vis, 0, sizeof(Vis));
  queue<pair<int, Point> > Q;
  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) >= B[nx][ny] || Vis[nx][ny])
        continue;
      Q.push({d + 1, {nx, ny}}), Vis[nx][ny] = true;
    }
  }
  return false;
}
int main() {
  cin >> N >> S;
  queue<Point> Q;
  Point Honey, Home;
  memset(B, -1, sizeof(B));
  _for(i, 0, N) {
    cin >> ws;
    _for(j, 0, N) {
      char& c = G[i][j];
      cin >> c;
      if (c == 'H') Q.push({i, j}), B[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) {
      Point np{p.x + DX[i], p.y + DY[i]};
      if (np.x < 0 || np.x >= N || np.y < 0 || np.y >= N ||
          G[np.x][np.y] != 'G' || B[np.x][np.y] != -1)
        continue;
      B[np.x][np.y] = B[p.x][p.y] + S, Q.push({np.x, np.y});
    }
  }
  B[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:57:21: warning: 'Home.Point::x' may be used uninitialized in this function [-Wmaybe-uninitialized]
   57 |   B[Home.x][Home.y] = N * N * S;
      |   ~~~~~~~~~~~~~~~~~~^~~~~~~~~~~
mecho.cpp:57:21: warning: 'Home.Point::y' may be used uninitialized in this function [-Wmaybe-uninitialized]

• Subtask 1: 100 / 100