Submission #977567

#	Time	Username	Problem	Language	Result	Execution time	Memory
977567		farica	Mecho (IOI09_mecho)	C++14	38 / 100	177 ms	6756 KiB

mecho

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

using namespace std;

const int MAX_N = 4e5 + 5;

int n, s, dist[805][805], sx, sy, ex, ey;
string grid[805];

bool test(int m) {
    queue<pair<int, pair<int,int>>>q;
    q.push({0, {sx, sy}});
    vector<vector<bool>>visited(n, vector<bool>(n, 0));
    while(!q.empty()) {
        int cnt = q.front().first, x = q.front().second.first, y = q.front().second.second;
        q.pop();
        if(visited[x][y]) continue;
        visited[x][y] = 1;
        ++cnt;
        int cost = cnt / s + (cnt % s > 0 ? 1 : 0) + m;
        if(x && dist[x-1][y] >= cost && grid[x-1][y] == 'G') q.push({cnt, {x-1, y}});
        if(y && dist[x][y-1] >= cost && grid[x][y-1] == 'G') q.push({cnt, {x, y-1}});
        if(x+1<n && dist[x+1][y] >= cost && grid[x+1][y] == 'G') q.push({cnt, {x+1, y}});
        if(y+1<n && dist[x][y+1] >= cost && grid[x][y+1] == 'G') q.push({cnt, {x, y+1}});
    }
    if(ex && visited[ex-1][ey]) return true;
    if(ey && visited[ex][ey-1]) return true;
    if(ex+1<n && visited[ex+1][ey]) return true;
    if(ey+1<n && visited[ex][ey+1]) return true;
    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;
            else if(grid[i][j] == 'D') ex=i, ey=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] == 'G') {
            dist[i-1][j] = dist[i][j] + 1;
            q.push({i-1, j});
        }
        if(j && dist[i][j-1] == -1 && grid[i][j-1] == 'G') {
            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] == 'G') {
            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] == 'G') {
            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+5, 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: 38 / 100