Submission #1094702

#	Time	Username	Problem	Language	Result	Execution time	Memory
1094702		akamizane	Mecho (IOI09_mecho)	C++17	100 / 100	170 ms	6884 KiB

mecho

#include<bits/stdc++.h>
 
using namespace std;
  
using pii = pair<int,int>;
#define REP(i, n) for (int i = 0; i < (n); i++)
#define fi first
#define se second

void solve(){
    int n, k;
    cin >> n >> k;
    string s[n];
    REP(i, n){
        cin >> s[i];
    }
    pii start, des;
    vector<vector<int>> dis(n, vector<int> (n ,1e9));
    queue<pii> q;
    REP(i, n){
        REP(j, n){
            if (s[i][j] == 'M'){
                start = {i, j};
            }
            if (s[i][j] == 'D'){
                des = {i, j};
            }
            if (s[i][j] == 'H'){
                q.push({i, j});
                dis[i][j] = 0;
            }
        }
    }
    int dx[4] = {0, 0, -1, 1};
    int dy[4] = {-1, 1, 0, 0};
    // bfs for bee 
    while(q.size()){
        auto [x, y] = q.front();
        q.pop();
        for (int i = 0; i < 4; i++){
            int a = x + dx[i], b = y + dy[i];
            if (a < 0 || a >= n || b < 0 || b >= n) continue;
            if (s[a][b] == 'T' || s[a][b] == 'D') continue;
            if (dis[x][y] + 1 < dis[a][b]){
                dis[a][b] = dis[x][y] + 1;
                q.push({a, b});
            } 
        }
    }
    auto check = [&](int m){
    
    if (dis[start.fi][start.se] <= m) return false;
    queue<pii> que;
    que.push(start);
    vector<vector<int>> dis2(n, vector<int> (n, 1e9));
    dis2[start.fi][start.se] = 0;
    while(que.size()){
        auto [x, y] = que.front();
        que.pop();
        if (x == des.fi && y == des.se) break;
        for (int i = 0; i < 4; i++){
            int a = x + dx[i], b = y + dy[i];
            if (a < 0 || a >= n || b < 0 || b >= n) continue;
            if (s[a][b] == 'T') continue;
            int cur = dis2[x][y];
            
            if ((cur + 1) / k < dis[a][b] - m && cur + 1 < dis2[a][b]){
                dis2[a][b] = cur + 1;
                que.push({a, b});
            }
        }
    }
    return dis2[des.fi][des.se] != 1e9;
};
  if (!check(0)){
    cout << -1;
    return;
  }
  // time must be lower than the time a bee touch start position
  int l = -1, r = dis[start.fi][start.se];
  while(r - l > 1){
    int mid = (l + r) / 2;
    if (check(mid)) l = mid;
    else r = mid;
  }
  cout << l;
}
 
int32_t main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  solve();
  return 0;
}

• Subtask 1: 100 / 100