Submission #652767

#	Time	Username	Problem	Language	Result	Execution time	Memory
652767		chanhchuong123	Mecho (IOI09_mecho)	C++14	42 / 100	1096 ms	11980 KiB

mecho

#pragma GCC optimize("Ofast")
#include <bits/stdc++.h>
using namespace std;
#define task "C"
#define fi first
#define se second

const int dx[] = {-1, 0, 0, +1};
const int dy[] = {0, -1, +1, 0};
const int N = 802;
int n, s;
char a[N][N];
pair<int, int> st, en;
pair<int, int> d[N][N];
pair<int, int> e[N][N];
deque<pair<int, int>> dq;

bool check(int time) {
  if (time >= d[st.fi][st.se].fi) return false;
  for (int i = 1; i <= n; i++) {
    for (int j = 1; j <= n; j++)
      e[i][j] = d[i][j];
  }
  while (dq.size()) dq.pop_back();
  e[st.fi][st.se] = {time, s};
  dq.push_back(st);
  while (dq.size()) {
    auto [u, v] = dq.front();
    int cnt = e[u][v].se;
    int du = e[u][v].fi;
    dq.pop_front();

    if (u == en.fi && v == en.se) return true;

    int w, _c;
    if (cnt == s) w = 1, _c = 1;
    else w = 0, _c = cnt + 1;

    for (int i = 0; i < 4; i++) {
      int x = u + dx[i], y = v + dy[i];
      if (x < 1 || x > n) continue;
      if (y < 1 || y > n) continue;
      if (a[x][y] != 'T') {
        if (e[x][y].fi > e[u][v].fi + w) {
          e[x][y].fi = e[u][v].fi + w;
          e[x][y].se = _c;
          if (w) dq.push_back({x, y});
          else dq.push_front({x, y});
        } else if (e[x][y].fi == e[u][v].fi + w) {
          if (_c == s && e[x][y].se == 0) continue;
          if (e[x][y].se == 0) {
            e[x][y].se = _c;
            if (w) dq.push_back({x, y});
            else dq.push_front({x, y});
          } else {
            if (e[x][y].se > _c) {
              e[x][y].se = _c;
              if (w) dq.push_back({x, y});
              else dq.push_front({x, y});
            }
          }
        }
      }
    }
  }
  return false;
}

int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0); cout.tie(0);

  cin >> n >> s;
  for (int i = 1; i <= n; i++)
    for (int j = 1; j <= n; j++)
      d[i][j] = {1e9, -1};
  for (int i = 1; i <= n; i++) {
    for (int j = 1; j <= n; j++) {
      cin >> a[i][j];
      if (a[i][j] == 'M')
      	st = make_pair(i, j);
      if (a[i][j] == 'D')
      	en = make_pair(i, j);
      if (a[i][j] == 'H') {
        d[i][j] = {0, 0};
        dq.push_back({i, j});
      }
    }
  }

  // FirstBfs();
  while (dq.size()) {
    auto [u, v] = dq.front();
    dq.pop_front();
    for (int i = 0; i < 4; i++) {
      int x = u + dx[i], y = v + dy[i];
      if (x < 1 || x > n) continue;
      if (y < 1 || y > n) continue;
      if (a[x][y] != 'T') {
        if (d[x][y].fi == 1e9) {
          d[x][y].fi = d[u][v].fi + 1;
          d[x][y].se = d[u][v].se;
          dq.push_back({x, y});
        }
      }
    }
  }

  int l = -1, r = n * n;
  while (r - l > 1) {
    int mid = l + r >> 1;
    if (check(mid)) l = mid;
    else r = mid;
  }
  cout << l;
}

Compilation message (stderr)

mecho.cpp: In function 'bool check(int)':
mecho.cpp:28:10: warning: structured bindings only available with '-std=c++17' or '-std=gnu++17'
   28 |     auto [u, v] = dq.front();
      |          ^
mecho.cpp:30:9: warning: unused variable 'du' [-Wunused-variable]
   30 |     int du = e[u][v].fi;
      |         ^~
mecho.cpp: In function 'int main()':
mecho.cpp:93:10: warning: structured bindings only available with '-std=c++17' or '-std=gnu++17'
   93 |     auto [u, v] = dq.front();
      |          ^
mecho.cpp:111:17: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
  111 |     int mid = l + r >> 1;
      |               ~~^~~

• Subtask 1: 42 / 100