Submission #977556

#	Time	Username	Problem	Language	Result	Execution time	Memory
977556		farica	Mecho (IOI09_mecho)	C++14	25 / 100	1099 ms	6744 KiB

mecho

#include <bits/stdc++.h>
#define int long long

using namespace std;

const int MAX_N = 4e5 + 5;

int n, s, dist[800][800], sx, sy;
string grid[800];

bool test(int m) {
    priority_queue<pair<int, pair<int,int>>>pq;
    vector<vector<bool>>visited(n, vector<bool>(n, 0));
    pq.push({0, {sx, sy}});
    while(!pq.empty()) {
        int x = pq.top().second.first, y = pq.top().second.second, cnt = -1 * pq.top().first;
        pq.pop();
        if(visited[x][y]) continue;
        visited[x][y] = 1;
        if(grid[x][y] == 'D') return true;
        int cost = ((cnt+1) / s) + ((cnt+1) % s > 0 ? 1 : 0) + m;
        if(x && grid[x-1][y] != 'T' && dist[x-1][y] >= cost) pq.push({(cnt + 1) * -1, {x-1, y}});
        if(y && grid[x][y-1] != 'T' && dist[x][y-1] >= cost) pq.push({(cnt + 1) * -1, {x, y-1}});
        if(x+1<n && grid[x+1][y] != 'T' && dist[x+1][y] >= cost) pq.push({(cnt + 1) * -1, {x+1, y}});
        if(y+1<n && grid[x][y+1] != 'T' && dist[x][y+1] >= cost) pq.push({(cnt + 1) * -1, {x, y+1}});
    }
    return false;
}

void solve() {
    cin >> n >> s;
    queue<pair<int,int>>q;
    for(int i=0; i<n; ++i) {
        cin >> grid[i];
        for(int j=0; j<n; ++j) {
            dist[i][j] = -1;
            if(grid[i][j] == 'H') {
                q.push({i, j});
                dist[i][j] = 0;
            } else if(grid[i][j] == 'M') sx=i, sy=j;
        }
    }
    while(!q.empty()) {
        int i = q.front().first, j = q.front().second;
        q.pop();
        if(i && dist[i-1][j] == -1 && grid[i-1][j] != 'T' && grid[i-1][j] != 'M') {
            dist[i-1][j] = dist[i][j] + 1;
            q.push({i-1, j});
        }
        if(j && dist[i][j-1] == -1 && grid[i][j-1] != 'T' && grid[i][j-1] != 'M') {
            dist[i][j-1] = dist[i][j] + 1;
            q.push({i, j-1});
        }
        if(i<n-1 && dist[i+1][j] == -1 && grid[i+1][j] != 'T' && grid[i+1][j] != 'M') {
            dist[i+1][j] = dist[i][j] + 1;
            q.push({i+1, j});
        }
        if(j<n-1 && dist[i][j+1] == -1 && grid[i][j+1] != 'T' && grid[i][j+1] != 'M') {
            dist[i][j+1] = dist[i][j] + 1;
            q.push({i, j+1});
        }
    }
    if(!test(0)) {
        cout << -1 << endl;
        return;
    }
    int l=0, r=n*n, mid;
    while(l<=r) {
        mid = (l+r)/2;
        if(test(mid)) l = mid + 1;
        else r = mid - 1;
    }
    cout << l - 1 << endl;
}

signed main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);

    int t = 1;
    while(t--) solve();

    return 0;
}

• Subtask 1: 25 / 100