Submission #1249206

#	Time	Username	Problem	Language	Result	Execution time	Memory
1249206		nanh0607	Mecho (IOI09_mecho)	C++20	30 / 100	178 ms	3912 KiB

mecho

#include <bits/stdc++.h>
#include <cstdlib>
using namespace std;
using ll = long long;
using str = string;
using pii = pair<int, int>;
using pil = pair<int, ll>;
using pll = pair<ll, ll>;
using tiii = tuple<int, int, int>;
#define FOR(i, l, r) for (int i=l; i<=r; i++)
#define FOR2(i, l, r) for (int i=l; i>=r; i--)
#define ALL(v) v.begin(), v.end()
#define RALL(v) v.rbegin(), v.rend()
#define fi first
#define se second
#define ce cout << endl
#define pb push_back
#define pf push_front
#define pob pop_back
#define eb emplace_back
#define ep emplace
const ll MOD = 998244353;
const int INF = 1e9;
const int LOG = 60;
const double MAX = 1e9;
int dx[4] = {-1, 1, 0, 0};
int dy[4] = {0, 0, 1, -1};
char direct[4] = {'U', 'D', 'R', 'L'};
// north, south, east, weast

void solve() {
    int n, k; cin >> n >> k;
    vector<str> forest(n);
    pii mecho, home;
    queue<pii> hive;
    vector<vector<int>> dist_bee(n, vector<int> (n, -1));

    FOR(i, 0, n-1) {
        cin >> forest[i];
        FOR(j, 0, n-1) {
            if (forest[i][j] == 'M') mecho = {i, j};
            else if (forest[i][j] == 'D') home = {i, j};
            else if (forest[i][j] == 'H') {
                hive.ep(i, j);
                dist_bee[i][j] = 0;
            }
        }
    }

    function<bool(int x, int y)> inside = [&] (int x, int y) {
        return x >= 0 && x < n && y >= 0 && y < n && forest[x][y] != 'T';
    };

    while (!hive.empty()) {
        auto [x1, y1] = hive.front(); hive.pop();
        // cout << x1 << ' ' << y1; ce;
        FOR(i, 0, 3) {
            int x2 = x1+dx[i], y2 = y1+dy[i];
            if (!inside(x2, y2) || dist_bee[x2][y2] != -1) continue;
            dist_bee[x2][y2] = dist_bee[x1][y1] + k;
            hive.ep(x2, y2);
        }
    }

    // FOR(i, 0, n-1) {
    //     FOR(j, 0, n-1) cout << dist_bee[i][j] << ' '; ce;
    // }

    function<bool(int minute)> bfs = [&] (int minute) {
        if (minute*k > dist_bee[mecho.fi][mecho.se]) return false;
        queue<pair<pii, int>> qe;
        vector<vector<bool>> vis(n, vector<bool> (n, false));
        qe.ep(mecho, minute*k);
        vis[mecho.fi][mecho.se] = true;

        while (!qe.empty()) {
            auto [p, t] = qe.front(); qe.pop();
            auto [x1, y1] = p;
            if (pii{x1, y1} == home) return true;
            FOR(i, 0, 3) {
                int x2 = x1+dx[i], y2 = y1+dy[i];
                if (!inside(x2, y2) || vis[x2][y2] || t+1 > dist_bee[x2][y2]) continue;
                qe.ep(pii{x2, y2}, t+1);
                vis[x2][y2] = true;
            }

            // cout << minute; ce;
            // FOR(i, 0, n-1) {
            //     FOR(j, 0, n-1) cout << vis[i][j] << ' '; ce;
            // } ce;
        }
        return false;
    };

    int low = -1, high = n*n;
    while (low < high) {
        int mid = (low + high + 1)/2;
        if (bfs(mid)) low = mid;
        else high = mid - 1;
    }
    cout << low;
}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(0); cout.tie(0);
    // freopen("atlarge.in", "r", stdin);
    // freopen("atlarge.out", "w", stdout);
    int t = 1;
    // cin >> t;
    while (t--) solve();
}

• Subtask 1: 30 / 100