Submission #839378

#	Time	Username	Problem	Language	Result	Execution time	Memory
839378		ArashJafariyan	Mecho (IOI09_mecho)	C++17	41 / 100	183 ms	6484 KiB

mecho

#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pii = pair<int, int>;

#define F first
#define S second
#define pb push_back
#define size(a) (int) a.size()
#define all(a) a.begin(), a.end()

const int maxn = 800 + 4, inf = 1e9;

int n, s, mx, my, dx, dy, d[maxn][maxn], save[maxn][maxn];
bitset<maxn> vis[maxn];
string a[maxn];
queue<array<int, 2>> q;

void rest() {
    for (int i = 0; i < n; ++i) {
        for (int j = 0; j < n; ++j) {
            vis[i][j] = 0;
            d[i][j] = inf;
        }
    }
    return;
}

bool check0(int x, int y, int dis) {
    bool ret = (0 <= x && x < n);
    ret &= (0 <= y && y < n);
    if (ret) {
        ret &= !vis[x][y];
        if (ret && a[x][y] == 'D') {
            d[x][y] = dis;
            vis[x][y] = 1;
            return 0;
        }
        ret &= (a[x][y] == 'G' || a[x][y] == 'M');
    }
    return ret;
}

void upd0(int x, int y) { 
    int dis = d[x][y] + 1;

    if (check0(x - 1, y, dis)) {
        vis[x - 1][y] = 1;
        d[x - 1][y] = dis;
        q.push({x - 1, y});
    }
    if (check0(x + 1, y, dis)) {
        vis[x + 1][y] = 1;
        d[x + 1][y] = dis;
        q.push({x + 1, y});
    }
    if (check0(x, y - 1, dis)) {
        vis[x][y - 1] = 1;
        d[x][y - 1] = dis;
        q.push({x, y - 1});
    }
    if (check0(x, y + 1, dis)) {
        vis[x][y + 1] = 1;
        d[x][y + 1] = dis;
        q.push({x, y + 1});
    }
}

bool check1(int x, int y, int dis, int k) {
    bool ret = (0 <= x && x < n);
    ret &= (0 <= y && y < n);
    if (ret) {
        ret &= !vis[x][y];
        ret &= a[x][y] == 'G' || a[x][y] == 'D';
        ret &= (dis + s - 1) / s <= save[x][y] - k;
    }
    return ret;
}

void upd1(int x, int y, int k) {
    int dis = d[x][y] + 1;
    
    if (check1(x - 1, y, dis, k)) {
        vis[x - 1][y] = 1;
        d[x - 1][y] = dis;
        q.push({x - 1, y});
    }
    if (check1(x + 1, y, dis, k)) {
        vis[x + 1][y] = 1;
        d[x + 1][y] = dis;
        q.push({x + 1, y});
    }
    if (check1(x, y - 1, dis, k)) {
        vis[x][y - 1] = 1;
        d[x][y - 1] = dis;
        q.push({x, y - 1});
    }
    if (check1(x, y + 1, dis, k)) {
        vis[x][y + 1] = 1;
        d[x][y + 1] = dis;
        q.push({x, y + 1});
    }
}

bool bfs(int k) {
    rest();

    if (save[mx][my] <= k) {
        return 0;
    }

    d[mx][my] = 0;
    vis[mx][my] = 1;
    q.push({mx, my});
    while (!q.empty()) {
        array<int, 2> v = q.front();
        q.pop();
        upd1(v[0], v[1], k);
    }
    
    return d[dx][dy] != inf;
}

int main() {
    ios::sync_with_stdio(0), cin.tie(0);

    cin >> n >> s;
    for (int i = 0; i < n; ++i) {
        cin >> a[i];
    }

    for (int i = 0; i < n; ++i) {
        for (int j = 0; j < n; ++j) {
            if (a[i][j] == 'H') {
                q.push({i, j});
                vis[i][j] = 1;
            }
        }
    }

    while (!q.empty()) {
        array<int, 2> v = q.front();
        q.pop();
        upd0(v[0], v[1]);
    }

    for (int i = 0; i < n; ++i) {
        for (int j = 0; j < n; ++j) {
            if (a[i][j] == 'M') {
                mx = i;
                my = j;
            }
            if (a[i][j] == 'D') {
                dx = i;
                dy = j;
            }
            save[i][j] = d[i][j];
        }
    }

    int l, r;
    l = -1;
    r = inf;

    while (r - l > 1) {
        int m = (l + r) >> 1;
        if (bfs(m)) {
            l = m;
        }
        else {
            r = m;
        }
    }
    cout << l << '\n';

    return 0;
}

• Subtask 1: 41 / 100