Submission #789665

#	Time	Username	Problem	Language	Result	Execution time	Memory
789665		phongcd	Mecho (IOI09_mecho)	C++14	100 / 100	145 ms	9416 KiB

mecho

#include <bits/stdc++.h>
#define ll long long
#define ld long  double
#define ull unsigned long long
#define ii pair <int, int>
#define ill pair <ll, ll>
#define fi first
#define se second
#define all(x) x.begin(), x.end()
#define file "test"
using namespace std;
const ll N = 8e2 + 2;
const ll MOD = 1e9;
const ll INF = 1e18;
const ll base = 311;
const int BLOCK_SIZE = 2000;
 
int n, s;
ii start, target, d[N][N];
bool vis[N][N];
char a[N][N];
int mtime[N][N];
int dx[4] = {-1, 1, 0, 0};
int dy[4] = {0, 0, -1, 1};
 
void addstep(ii &a) {
    a.se += 1;
    if (a.se == s) a.fi ++, a.se = 0;
}

bool cmp2(ii a, int b) {
    if (a.fi != b) return a.fi < b;
    return a.se < s;
}
 
bool check(int x) {
    if (x >= mtime[start.fi][start.se]) return 0;

    memset(vis, 0, sizeof vis);
    for (int i = 1; i <= n; i ++)
        for (int j = 1; j <= n; j ++) d[i][j] = {2e9, 0};

    queue <ii> h;
    h.push(start);
    d[start.fi][start.se] = {x + 1, 0};
    vis[start.fi][start.se] = 1;
 
    while (!h.empty()) {
        ii e = h.front(); h.pop();
        int x = e.fi, y = e.se;
        ii res = d[x][y];
        addstep(res);
 
        for (int j = 0; j <= 3; j ++) {
            int u = x + dx[j];
            int v = y + dy[j];
            if (a[u][v] == 'G' && cmp2(res, mtime[u][v]) && !vis[u][v]) {
                h.push({u, v});
                d[u][v] = res;
                vis[u][v] = 1;
            }
        }
    }
    return d[target.fi][target.se].fi != 2e9;
}
 
int main() {
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);

    cin >> n >> s;
    queue <ii> bee;
    for (int i = 1; i <= n; i ++)
        for (int j = 1; j <= n; j ++) {
            cin >> a[i][j]; 
            mtime[i][j] = 2e9;
 
            if (a[i][j] == 'H') 
                bee.push({i, j}), mtime[i][j] = 0;
 
            if (a[i][j] == 'M')
                a[i][j] = 'G', start = {i, j};
 
            if (a[i][j] == 'D') 
                target = {i, j};
        }
 
    while (!bee.empty()) {
        ii e = bee.front(); bee.pop();
        int x = e.fi, y = e.se;
        int res = mtime[x][y] + 1;
 
        for (int j = 0; j <= 3; j ++) {
            int u = x + dx[j];
            int v = y + dy[j];
            if (a[u][v] == 'G' && mtime[u][v] > res) {
                bee.push({u, v});
                mtime[u][v] = res;
            }
        }
    }
    a[target.fi][target.se] = 'G';

    int l = 0, r = 1e9;
    while (l < r) {
        int mid = l + (r - l + 1) / 2;
        if (check(mid)) l = mid;
        else r = mid - 1;
    }
    cout << (check(l) ? l : -1) << '\n';
}
/*
     /\_/\ zzZ
    (= -_-)
    / >u  >u
*/

• Subtask 1: 100 / 100