Submission #953268

#	Time	Username	Problem	Language	Result	Execution time	Memory
953268		dpsaveslives	Mecho (IOI09_mecho)	C++17	68 / 100	151 ms	9000 KiB

mecho

#include <bits/stdc++.h>
#define f first
#define s second
using namespace std;
const int MAXN = 810;
char grid[MAXN][MAXN];
int dr[4] = {0,0,1,-1}, dc[4] = {1,-1,0,0},N;
bool goodbees(int r, int c){
    return r >= 0 && c >= 0 && r <= N-1 && c <= N-1 && grid[r][c] != 'T' && grid[r][c] != 'D';
}
bool goodmecho(int r, int c){
    return r >= 0 && c >= 0 && r <= N-1 && c <= N-1 && grid[r][c] != 'T';
}
const int INF = 1e9;
int main()
{
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
    int S; cin >> N >> S;
    queue<pair<int,int>> q;
    vector<vector<int>> dist(N,vector<int>(N,INF));
    pair<int,int> m,home;
    for(int i = 0;i<N;++i){
        for(int j = 0;j<N;++j){
            cin >> grid[i][j];
            if(grid[i][j] == 'H'){
                q.push({i,j});
                dist[i][j] = 0;
            }
            else if(grid[i][j] == 'M'){
                m.f = i, m.s = j;
            }
            else if(grid[i][j] == 'D'){
                home.f = i, home.s = j;
            }
        }
    }
    while(!q.empty()){
        int r = q.front().f, c = q.front().s; q.pop();
        for(int i = 0;i<4;++i){
            int nr = r+dr[i], nc = c+dc[i];
            if(goodbees(nr,nc)){
                if(dist[nr][nc] > dist[r][c]+1){
                    dist[nr][nc] = dist[r][c]+1;
                    q.push({nr,nc});
                }
            }
        }
    }
    /*vector<vector<int>> mecho(N,vector<int>(N,INF));
    mecho[m.f][m.s] = 0; q.push(m);
    while(!q.empty()){
        int r = q.front().f, c = q.front().s; q.pop();
        for(int i = 0;i<4;++i){
            int nr = r+dr[i], nc = c+dc[i];
            if(goodmecho(nr,nc)){
                if(mecho[nr][nc] > mecho[r][c]+1){
                    mecho[nr][nc] = mecho[r][c]+1;
                    q.push({nr,nc});
                }
            }
        }
    }*/
    int lo = 0, hi = INF;
    if(hi < 0){
        cout << "-1\n";
        return 0;
    }
    vector<vector<int>> D(N,vector<int>(N,INF));
    while(lo < hi){
        int mid = lo+(hi-lo+1)/2; //time
        //cout << mid << "\n";
        D = vector<vector<int>>(N,vector<int>(N,INF));
        q.push(m); D[m.f][m.s] = 0;
        while(!q.empty()){
            int r = q.front().f, c = q.front().s; q.pop();
            //cout << r << " " << c << "\n";
            for(int i = 0;i<4;++i){
                int nr = r+dr[i], nc = c+dc[i];
                if(goodmecho(nr,nc)){
                    if((D[r][c]+1)/S +mid < dist[nr][nc] && D[r][c]+1 < D[nr][nc]){
                        D[nr][nc] = D[r][c]+1;
                        q.push({nr,nc});
                    }
                }
            }
        }
        if(D[home.f][home.s] == INF){
            hi = mid-1;
        }
        else{
            lo = mid;
        }
    }
    cout << lo << "\n";
    return 0;
}

• Subtask 1: 68 / 100