Submission #739768

#	Time	Username	Problem	Language	Result	Execution time	Memory
739768		gigabuffoon	Mecho (IOI09_mecho)	C++17	100 / 100	242 ms	16304 KiB

mecho

#include<bits/stdc++.h>
using namespace std;
#define all(a) begin(a), end(a)
#define sz(a) (int)(size(a))
#define rep(i,a,b) for(int i=(a);i<(b);++i)
#define int long long
using vi = vector<int>;
using vvi = vector<vi>;
using pii = pair<int,int>;

#define CASES 0

int N, S;
int dr[4] = {1, 0, -1, 0};
int dc[4] = {0, 1, 0, -1};

const int MAXN = 800;
string grid[MAXN];
pii start, finish;
int wall[MAXN][MAXN];
int bee[MAXN][MAXN];

inline bool inBounds(const int r, const int c) {
    return 0 <= r and r < N and 0 <= c and c < N and !wall[r][c];
}

void solve(int tc) {
    cin >> N >> S;
    
    rep(i,0,N) cin >> grid[i];

    rep(i,0,N) rep(j,0,N) bee[i][j] = 1L << 40;

    queue<pii> bq;
    rep(i,0,N) rep(j,0,N) switch(grid[i][j]) {
        case 'T':
            wall[i][j] = 1;
            break;
        case 'M':
            start = {i, j};
            break;
        case 'D':
            wall[i][j] = 1;
            finish = {i, j};
            break;
        case 'H':
            bee[i][j] = 0;
            bq.emplace(i, j);
            break;
    }

    // bee-FS
    while(sz(bq)) {
        int r, c, rr, cc;
        tie(r, c) = bq.front(); bq.pop();
        rep(d,0,4) if(inBounds(rr = r + dr[d], cc = c+dc[d]))
            if(bee[r][c] + S < bee[rr][cc])
                bee[rr][cc] = bee[r][c] + S,
                bq.emplace(rr, cc);
    }

    wall[finish.first][finish.second] = 0;

    auto test = [&](int delay) {
        vvi dist(N, vi(N, 1L << 40));
        queue<pii> mq; mq.push(start);
        dist[start.first][start.second] = delay * S;
        if(delay * S >= bee[start.first][start.second]) return false;

        while(sz(mq)) {
            if(mq.front() == finish) return true;

            int r, c, rr, cc;
            tie(r, c) = mq.front(); mq.pop();
            rep(d,0,4) if(inBounds(rr = r + dr[d], cc = c+dc[d]))
            if(dist[r][c]+1 < dist[rr][cc] and dist[r][c]+1 < bee[rr][cc])
                dist[rr][cc] = dist[r][c] + 1,
                mq.emplace(rr, cc);
        }

        return false;
    };

    int res = -1;
    for(int x = 1 << 21; x; x >>= 1)
        if(test(res+x)) res += x;
    cout << res << '\n';

}

signed main() {
    ios::sync_with_stdio(false), cin.tie(0);
    int T = 1, t = 0; if(CASES) cin >> T;
    while(t++ < T) solve(t);
    return 0;
}

• Subtask 1: 100 / 100