Submission #1212580

#	Time	Username	Problem	Language	Result	Execution time	Memory
1212580		spampots	Mecho (IOI09_mecho)	C++20	29 / 100	155 ms	6208 KiB

mecho

#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<pii> vpii;

const int MOD = 1e9 + 7;
const int INF = INT_MAX;
const ll LINF = LLONG_MAX;

#define fast ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL)

#define pb push_back
#define mp make_pair
#define fi first
#define se second
#define all(v) v.begin(), v.end()
#define rep(i, a, b) for(int i = a; i < b; ++i)

void solve() {
    int N, S;
    cin >> N >> S;

    vector<vector<char>> grid(N, vector<char>(N));
    vector<vector<int>> dB(N, vector<int>(N, INF));
    queue<pii> bees;
    pii start, end;
    for(int i = 0; i < N; ++i) {
        for(int j = 0; j < N; ++j) {
            cin >> grid[i][j];
            if(grid[i][j] == 'H') {
                bees.push({i, j});
                dB[i][j] = 0;
            }
            if(grid[i][j] == 'M') {
                start = {i, j};
                grid[i][j] = 'G'; // Mark as walkable after start
            }
            if(grid[i][j] == 'D') {
                end = {i, j};
            }
        }
    }

    // BFS to calculate bees' movement times
    int dx[] = {1, -1, 0, 0};
    int dy[] = {0, 0, 1, -1};
    while(!bees.empty()) {
        auto [x, y] = bees.front();
        bees.pop();
        for(int k = 0; k < 4; ++k) {
            int nx = x + dx[k];
            int ny = y + dy[k];
            if(nx >= 0 && nx < N && ny >= 0 && ny < N && grid[nx][ny] != 'T' && grid[nx][ny] != 'D' && dB[nx][ny] == INF) {
                dB[nx][ny] = dB[x][y] + 1;
                bees.push({nx, ny});
            }
        }
    }

    int ans = -1;
    int lo = -1, hi = N * N;
    while(lo <= hi) {
        int mid = lo + (hi - lo) / 2;
        queue<pii> q;
        vector<vector<int>> d(N, vector<int>(N, INF));
        if(dB[start.fi][start.se] > mid) {
            d[start.fi][start.se] = 0;
            q.push(start);
        }
        bool found = false;
        while(!q.empty() && !found) {
            auto [x, y] = q.front();
            q.pop();
            for(int k = 0; k < 4; ++k) {
                int nx = x + dx[k];
                int ny = y + dy[k];
                if(nx >= 0 && nx < N && ny >= 0 && ny < N) {
                    if(grid[nx][ny] == 'D') {
                        found = true;
                        break;
                    }
                    if(grid[nx][ny] != 'T' && grid[nx][ny] != 'H' && d[nx][ny] == INF) {
                        int bear_time = d[x][y] + 1;
                        int steps = (bear_time + S - 1) / S;
                        if(dB[nx][ny] > mid + steps) {
                            d[nx][ny] = bear_time;
                            q.push({nx, ny});
                        }
                    }
                }
            }
            if(found) break;
        }
        if(found) {
            ans = mid;
            lo = mid + 1;
        } else {
            hi = mid - 1;
        }
    }
    cout << ans + 1 << endl;
}

int main() {
    fast;

    int t = 1;
    while(t--) {
        solve();
    }

    return 0;
}

• Subtask 1: 29 / 100