Submission #636758

#	Time	Username	Problem	Language	Result	Execution time	Memory
636758		wyhong3103	Mecho (IOI09_mecho)	C++14	94 / 100	551 ms	6456 KiB

mecho

#include <bits/stdc++.h>
#define all(x) begin(x),end(x)
#define fir first
#define sec second
#define sz(x) x.size()
#define pb push_back
 
using namespace std;
using ll = long long;
using vi = vector<int>;
using pi = pair<int,int>;
using pdb = pair<double,double>;
using pll = pair<ll,ll>;
using vll = vector<ll>;
const double EPS = (1e-6);
 
void setio(string s){
    freopen((s + ".in").c_str(),"r",stdin);
    freopen((s + ".out").c_str(),"w",stdout);
}

vi dr = {1, -1, 0, 0};
vi dc = {0, 0, 1, -1};


bool valid(int ans, int n, int s,pi m, vector<pi>& hives, vector<string>& grid){
    bool ok = 1;

    //1 = mecho, -1 = bee
    vector<vi> occupy(n, vi(n));
    vector<vi> dist(n, vi (n, -1));

    queue<pi> bees;
    for(auto& i :hives){
        bees.push(i);
        dist[i.fir][i.sec] = 0;
        occupy[i.fir][i.sec] = -1;
    }

    while (!bees.empty()){
        pi cur = bees.front(); 
        if (cur == m) ok = 0;
        if (dist[cur.fir][cur.sec] == ans){
            break;
        }
        bees.pop();


        for(int i{}; i < 4; i++){
            if (cur.fir+dr[i] < 0 || cur.fir+dr[i] >= n || cur.sec+dc[i] < 0 || cur.sec+dc[i] >= n) continue;
                if (occupy[cur.fir+dr[i]][cur.sec+dc[i]] >= 0 && grid[cur.fir+dr[i]][cur.sec+dc[i]] != 'T' && grid[cur.fir+dr[i]][cur.sec+dc[i]] != 'D'){
                occupy[cur.fir+dr[i]][cur.sec+dc[i]] = -1;
                dist[cur.fir+dr[i]][cur.sec+dc[i]] = dist[cur.fir][cur.sec]+1;
                bees.push({cur.fir+dr[i], cur.sec+dc[i]});
            }
        } 
    }
    
    int cur_time = ans+1;
    bool found = 0;
    
    queue<pi> mecho;
    mecho.push(m);
    dist[m.fir][m.sec] = 0;
    occupy[m.fir][m.sec] = 1;

    while (!found && ok && !mecho.empty() && !bees.empty()){
        while (!mecho.empty()){
            pi cur = mecho.front();

            if (occupy[cur.fir][cur.sec] == -1){
                mecho.pop();
                continue;
            }
            if (dist[cur.fir][cur.sec] == (cur_time-ans)*s) break;
            mecho.pop();

            for(int i{}; i < 4; i++){
                if (cur.fir+dr[i] < 0 || cur.fir+dr[i] >= n || cur.sec+dc[i] < 0 || cur.sec+dc[i] >= n) continue;
                if (occupy[cur.fir+dr[i]][cur.sec+dc[i]] == 0 && grid[cur.fir+dr[i]][cur.sec+dc[i]] != 'T'){
                    occupy[cur.fir+dr[i]][cur.sec+dc[i]] = 1;
                    dist[cur.fir+dr[i]][cur.sec+dc[i]] = dist[cur.fir][cur.sec]+1;
                    mecho.push({cur.fir+dr[i], cur.sec+dc[i]});
                }
                if (grid[cur.fir+dr[i]][cur.sec+dc[i]] == 'D'){
                    found = 1;
                    break;
                }
            }
        }

        while (!bees.empty()){
            pi cur = bees.front(); 
            if (dist[cur.fir][cur.sec] == cur_time){
                break;
            }
            bees.pop();

            for(int i{}; i < 4; i++){
                if (cur.fir+dr[i] < 0 || cur.fir+dr[i] >= n || cur.sec+dc[i] < 0 || cur.sec+dc[i] >= n) continue;
                if (occupy[cur.fir+dr[i]][cur.sec+dc[i]] >= 0 && grid[cur.fir+dr[i]][cur.sec+dc[i]] != 'T' && grid[cur.fir+dr[i]][cur.sec+dc[i]] != 'D'){
                    occupy[cur.fir+dr[i]][cur.sec+dc[i]] = -1;
                    dist[cur.fir+dr[i]][cur.sec+dc[i]] = dist[cur.fir][cur.sec]+1;
                    bees.push({cur.fir+dr[i], cur.sec+dc[i]});
                }
            } 
        }

        cur_time++;
    /*
    for(int i{}; i < n; i++){
        for(int j{};j  < n; j++){
            cout << dist[i][j] << '\t';
        }
        cout << '\n';
    }
    cout << '\n';

    for(int i{}; i < n; i++){
        for(int j{};j  < n; j++){
            cout << occupy[i][j] << '\t';
        }
        cout << '\n';
    }
    cout << '\n';
    */
    }

    return (found && ok);
}


void solve(){
    int n, s;
    cin >> n >> s;

    vector<string> grid(n);
    for(auto& i : grid) cin >> i;

    vector<pi> hives;
    pi m;
    for(int i{}; i < n; i++){
        for(int j{};j < n; j++){
            if (grid[i][j] == 'M') m = {i,j};
            else if (grid[i][j] == 'H'){
                hives.pb({i,j});
            }
        }
    }

    int lo = 0, hi = n*n;
    
    while (hi > lo){
        int mid = lo + (hi-lo+1)/2;
        if (valid(mid, n, s, m, hives, grid)){
            lo = mid;
        }else hi = mid-1;
    }

    cout << (valid(lo,n,s,m,hives,grid) ? lo : -1);
}

int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    int t = 1;
    while(t--){
        solve();
    }
    return 0;
}

Compilation message (stderr)

mecho.cpp: In function 'void setio(std::string)':
mecho.cpp:18:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   18 |     freopen((s + ".in").c_str(),"r",stdin);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
mecho.cpp:19:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   19 |     freopen((s + ".out").c_str(),"w",stdout);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 94 / 100