Submission #508812

#	Time	Username	Problem	Language	Result	Execution time	Memory
508812		tabr	Mecho (IOI09_mecho)	C++17	100 / 100	173 ms	7000 KiB

mecho

#include <bits/stdc++.h>
using namespace std;
#ifdef tabr
#include "library/debug.cpp"
#else
#define debug(...)
#endif

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    int n, m;
    cin >> n >> m;
    vector<string> s(n);
    for (int i = 0; i < n; i++) {
        cin >> s[i];
    }
    vector<vector<int>> a(n, vector<int>(n, -1));
    queue<int> que;
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < n; j++) {
            if (s[i][j] == 'H') {
                a[i][j] = 0;
                que.emplace(i * n + j);
            } else if (s[i][j] == 'D' || s[i][j] == 'T') {
                a[i][j] = 0;
            }
        }
    }
    vector<int> dx = {1, 0, -1, 0};
    vector<int> dy = {0, 1, 0, -1};
    while (!que.empty()) {
        int x = que.front() / n;
        int y = que.front() % n;
        que.pop();
        for (int dir = 0; dir < 4; dir++) {
            int nx = x + dx[dir];
            int ny = y + dy[dir];
            if (min(nx, ny) < 0 || max(nx, ny) >= n || a[nx][ny] != -1) {
                continue;
            }
            a[nx][ny] = a[x][y] + 1;
            que.emplace(nx * n + ny);
        }
    }
    int sx = -1;
    int sy = -1;
    int tx = -1;
    int ty = -1;
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < n; j++) {
            if (s[i][j] == 'M') {
                sx = i;
                sy = j;
            } else if (s[i][j] == 'D') {
                tx = i;
                ty = j;
            }
        }
    }
    debug(a);
    int lo = -1;
    int hi = a[sx][sy];
    while (hi - lo > 1) {
        int mid = (hi + lo) / 2;
        vector<vector<int>> b(n, vector<int>(n, -1));
        que.emplace(sx * n + sy);
        b[sx][sy] = 0;
        while (!que.empty()) {
            int x = que.front() / n;
            int y = que.front() % n;
            que.pop();
            for (int dir = 0; dir < 4; dir++) {
                int nx = x + dx[dir];
                int ny = y + dy[dir];
                if (nx == tx && ny == ty) {
                    b[tx][ty] = 0;
                    break;
                }
                if (min(nx, ny) < 0 || max(nx, ny) >= n || b[nx][ny] != -1 || b[x][y] + 1 >= m * (a[nx][ny] - mid)) {
                    continue;
                }
                b[nx][ny] = b[x][y] + 1;
                que.emplace(nx * n + ny);
            }
        }
        if (b[tx][ty] != -1) {
            lo = mid;
        } else {
            hi = mid;
        }
    }
    cout << lo << '\n';
    return 0;
}

• Subtask 1: 100 / 100