Submission #1263117

#	Time	Username	Problem	Language	Result	Execution time	Memory
1263117		dhuyyyy	Mecho (IOI09_mecho)	C++20	100 / 100	139 ms	12100 KiB

mecho

#include <bits/stdc++.h>
#define fi first
#define se second
#define int long long
using namespace std;

using ll = long long;
using ii = pair<int,int>;
using pii = pair<int,ii>;
using aa = array<int,4>;

const int N = 805;
const int INF = 1e9;
const int MOD = 1e9+21;

int n,S,c,u,v,start_x,start_y,home_x,home_y;
int ans = -1,cur = -1;
int Mecho[N][N],Bee[N][N];
bool vis[N][N],okay;
int dx[4] = {1,0,-1,0};
int dy[4] = {0,1,0,-1};
char a[N][N];
queue <ii> q;

bool reached(int a,int b){
    return a / S < b;
}
bool ok(int i,int j){
    return min(i,j) >= 1 && max(i,j) <= n && a[i][j] != 'H' && a[i][j] != 'T';
}
bool check(int mid){
    while (!q.empty()) q.pop();
    q.push({start_x,start_y});
    if (!reached(0,Bee[start_x][start_y] - mid)) return 0;
    Mecho[start_x][start_y] = 0;
    okay = 0;
    for (int i = 1; i <= n; i++){
        for (int j = 1; j <= n; j++) vis[i][j] = 0;
    }
    vis[start_x][start_y] = 1;
    while (!q.empty()){
        tie(u,v) = q.front();
        if (u == home_x && v == home_y) return 1;
        q.pop();
        for (int k = 0; k < 4; k++){
            int x = u + dx[k];
            int y = v + dy[k];
            if (ok(x,y) && !vis[x][y] && reached(Mecho[u][v]+1,Bee[x][y] - mid)){
                Mecho[x][y] = Mecho[u][v] + 1;
                vis[x][y] = 1;
                q.push({x,y});
            }
        }
    }
    return 0;
}
signed main(){
    ios_base::sync_with_stdio(false);
    cin.tie(NULL); cout.tie(NULL);
    cin >> n >> S;
    for (int i = 1; i <= n; i++){
        for (int j = 1; j <= n; j++){
            cin >> a[i][j];
            if (a[i][j] == 'M'){ //Mecho pos
                start_x = i;
                start_y = j;
            }
            if (a[i][j] == 'H'){ //Hives pos
                q.push({i,j});
                vis[i][j] = 1;
            }
            if (a[i][j] == 'D'){ //Mecho home
                home_x = i;
                home_y = j;
                Bee[i][j] = 1e9+5;
            }
        }
    }
    while (!q.empty()){
        tie(u,v) = q.front();
        q.pop();
        for (int k = 0; k < 4; k++){
            int x = u + dx[k];
            int y = v + dy[k];
            if (ok(x,y) && !vis[x][y] && a[x][y] != 'D'){
                Bee[x][y] = Bee[u][v] + 1;
                vis[x][y] = 1;
                q.push({x,y});
            }
        }
    }
    int l = 0,r = n*n,ans = -1;
    while(l <= r){
        int mid = (l + r) >> 1;
        if (check(mid)){
            ans = mid;
            l = mid + 1;
        } else r = mid - 1;
    }
    cout << ans;
    return 0;
}

• Subtask 1: 100 / 100