Submission #636906

#	Time	Username	Problem	Language	Result	Execution time	Memory
636906		ojoConmigo	Mecho (IOI09_mecho)	C++17	23 / 100	1100 ms	27928 KiB

mecho

#include <bits/stdc++.h>
using namespace std;

int n,s;
vector<vector<char>> grid;
vector<pair<int,int>> hives;
pair<int,int> root,obj;
vector<vector<int>> mapa;
vector<vector<bool>> visit;
vector<vector<int>> dp;

int sx[4] = {0,0,1,-1};
int sy[4] = {1,-1,0,0};

bool ok(int x, int y){
    return x < n && y < n && x >= 0 && y >= 0;
}

void bfs(){
    queue<pair<int,int>> cola;
    for(auto h : hives){
        cola.push(h);
    }
    while(cola.size()){
        auto q = cola.front();
        cola.pop();
        int x = q.first;
        int y = q.second;
        for(int i=0; i<4; i++){
            int nx = x + sx[i];
            int ny = y + sy[i];
            if(ok(nx,ny)){
                if(mapa[nx][ny] != -1)continue;
                if(grid[nx][ny] == 'G' || grid[nx][ny] == 'M'){
                    mapa[nx][ny] = mapa[x][y]+1;
                    cola.push({nx,ny});
                }
            }
        }
    }
}
/*
bool dfs(int x, int y,int k){
    if(x == obj.first && y == obj.second)return true;
    visit[x][y] = true;
    bool b = false;
    for(int i=0; i<4; i++){
        int nx = x+sx[i];
        int ny = y+sy[i];
        if(ok(nx,ny)){
            if(grid[nx][ny] == 'G' || grid[nx][ny] == 'D'){
                if(visit[nx][ny]) continue;
                if(mapa[nx][ny] > k){
                    b = max(b,dfs(nx,ny,k));
                }
            }
        }
    }
    return b;
}
*/
int dfs(int x, int y,int cost, int steps){
    //cout << x << " " << y << " " << cost << " " << steps << endl;
    //cout << dp[x][y] << endl;
    if(x == obj.first && y == obj.second) return 1e9;
    if(mapa[x][y] - cost < 0) return -1;
    if(dp[x][y] >= mapa[x][y] - cost) return -1;
    dp[x][y] = mapa[x][y] - cost;
    if(steps == s){
        steps = 0;
        cost++;
    }
    int sol = -1;
    for(int i=0; i<n; i++){
        int nx = x+sx[i];
        int ny = y+sy[i];
        if(ok(nx,ny)){
            if(grid[nx][ny] == 'G' || grid[nx][ny] == 'D'){
                int k = dfs(nx,ny,cost,steps+1);
                sol = max(sol,k);
                //cout << nx << " " << ny << " k: " << k << " sol: " << sol << endl;
            }
        }
    }
    //cout << x << " " << y << " " << cost << " sol: " << sol << endl;
    if(sol != -1) return min(sol,dp[x][y]);
    return -1;
}

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

    cin >> n >> s;
    grid.assign(n,vector<char> (n));
    mapa.assign(n,vector<int>(n,-1));
    for(int i=0; i<n; i++){
        for(int j=0; j<n; j++){
            cin >> grid[i][j];
            if(grid[i][j] == 'H'){
                hives.push_back({i,j});
                mapa[i][j] = 0;
            }
            if(grid[i][j] == 'M'){
                root = {i,j};
            }
            if(grid[i][j] == 'D'){
                obj = {i,j};
            }
        }
    }

    bfs();
    /*
    for(int i=0; i<n; i++){
        for(int j=0; j<n; j++){
            cout << mapa[i][j] << " ";
        }
        cout << endl;
    }
    */

    dp.assign(n,vector<int>(n,-1));
    cout << dfs(root.first,root.second,1,0) << endl;
    return 0;
    /*
    int lo = 1, hi = n*n, res = -1;
    while(lo <= hi){
        int mid = (lo+hi)/2;
        int k = dfs(root.first,root.second,s*mid);
        if(k - mid > res){
            res = mid;
            lo = mid+1;
        }else hi = mid-1;
    }
    cout << res << endl;
    */
}

• Subtask 1: 23 / 100