Submission #1208591

#	Time	Username	Problem	Language	Result	Execution time	Memory
1208591		timeflew	Mecho (IOI09_mecho)	C++20	27 / 100	129 ms	4512 KiB

mecho

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

const int mxN = 8e2;
char c[mxN][mxN];
int vis[mxN][mxN];
bool vis1[mxN][mxN];
pair<int, int> st, ed;
int n, s;
int dx[4] = {0, 0, 1, -1};
int dy[4] = {1, -1, 0, 0};

bool mecho_valid(int x, int y) {
    return x >= 0 && x < n && y >= 0 && y < n && 
           (c[x][y] == 'G' || c[x][y] == 'M' || c[x][y] == 'D');
}

bool bee_valid(int x, int y) {
    return x >= 0 && x < n && y >= 0 && y < n && 
           (c[x][y] == 'G' || c[x][y] == 'M');
}

bool check(int x) {
    if (vis[st.first][st.second] <= x) return 0; // Bees reach 'M' during eating
    queue<array<int, 4>> q; // {x, y, minute, steps_in_minute}
    q.push({st.first, st.second, x + 1, 0});
    memset(vis1, 0, sizeof(vis1));
    vis1[st.first][st.second] = 1;
    while (!q.empty()) {
        auto [xx, yy, step, state] = q.front();
        q.pop();
        if (xx == ed.first && yy == ed.second) return 1;
        for (int i = 0; i < 4; i++) {
            int nx = xx + dx[i], ny = yy + dy[i];
            if (mecho_valid(nx, ny) && vis[nx][ny] > step && !vis1[nx][ny]) {
                vis1[nx][ny] = 1;
                if (state + 1 == s) {
                    q.push({nx, ny, step + 1, 0});
                } else {
                    q.push({nx, ny, step, state + 1});
                }
            }
        }
    }
    return 0;
}

int main() {
    ios::sync_with_stdio(0); cin.tie(0);
    cin >> n >> s;
    queue<array<int, 3>> q;
    memset(vis, 0x3f, sizeof(vis));
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < n; j++) {
            cin >> c[i][j];
            if (c[i][j] == 'M') st = {i, j};
            if (c[i][j] == 'D') ed = {i, j};
            if (c[i][j] == 'H') q.push({i, j, 0}), vis[i][j] = 0;
        }
    }
    while (!q.empty()) {
        auto [x, y, now] = q.front();
        q.pop();
        for (int i = 0; i < 4; i++) {
            int nx = x + dx[i], ny = y + dy[i];
            if (bee_valid(nx, ny) && vis[nx][ny] == 0x3f3f3f3f) {
                vis[nx][ny] = now + 1;
                q.push({nx, ny, now + 1});
            }
        }
    }
    int l = 0, r = n * n, ans = -1;
    while (l <= r) {
        int mid = (l + r) / 2;
        if (check(mid)) {
            ans = mid;
            l = mid + 1;
        } else {
            r = mid - 1;
        }
    }
    cout << ans << "\n";
    return 0;
}

• Subtask 1: 27 / 100