Submission #958047

#	Time	Username	Problem	Language	Result	Execution time	Memory
958047		theehann	Mecho (IOI09_mecho)	C++17	69 / 100	150 ms	11712 KiB

mecho

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define int ll
#define ft first
#define se second
#define NAME "A"
#define file freopen(NAME".INP","r",stdin); freopen(NAME".OUT","w",stdout);
#define sdf ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
const int MOD = 1e9 + 7;
const int N = 800 + 5, INF = 1e15;

int dx[4] = {0, 0, -1, 1};
int dy[4] = {-1, 1, 0, 0};
char a[N][N];
int dis[N][N], vis[N][N] = {INF};
bool f = false;
int n, step, homex, homey, mx, my;

bool bfs(int len, int x, int y){
	vis[x][y] = len;
	queue<tuple<int, int, int>> q;
	q.push({x, y, 0});
	while(!q.empty()){
		const auto [sx, sy, cur] = q.front(); q.pop();
		int dist = (cur + 1) / step;

		for(int i = 0;i < 4;++i){
			int u = sx + dx[i], v = sy + dy[i];
			if(u < 1 || v < 1 || v > n || u > n) continue;
			if(a[u][v] == 'G' && (cur + 1) < vis[u][v] && dist < dis[u][v] - (len / step)){
				vis[u][v] = cur + 1;
				q.push({u, v, cur + 1});
			}
		}
	}

	for(int i = 0;i < 4;++i){
		int u = homex + dx[i], v = homey + dy[i];
		if(vis[u][v] != INF && (a[u][v] == 'G' || a[u][v] == 'M') && vis[u][v] / step < dis[u][v] - (len / step)){
			return true;
		}
	}
	return false;
}

int32_t main(){
	sdf
	cin >> n >> step;
	queue<pair<int, int>> q;
	for(int i = 1;i <= n;++i){
		for(int j = 1;j <= n;++j){
			cin >> a[i][j];
			dis[i][j] = INF;
			if(a[i][j] == 'H'){
				q.push({i, j});
				dis[i][j] = 0;
			}
			else if(a[i][j] == 'D'){
				homex = i; homey = j;
			}
			else if(a[i][j] == 'M'){
				mx = i; my = j;
			}
		}
	}

	while(!q.empty()){
		const auto [x, y] = q.front(); q.pop();

		for(int i  = 0;i < 4;++i){
			int u = x + dx[i];
			int v = y + dy[i];
			if(u < 1 || v < 1 || u > n || v > n) continue;
			if(dis[u][v] == INF && (a[u][v] == 'G' || a[u][v] == 'M')){
				dis[u][v] = dis[x][y] + 1;
				q.push({u, v});
			}
		}
	}

	int l = 1, r = INF;
	int ans =0;
	while(l <= r){
		int mid = (l + r) / 2;
		for(int i = 1;i <= n;++i){
			for(int j = 1;j <= n;++j){
				vis[i][j] = INF;
			}
		}
		if(bfs(mid * step, mx, my)){
			l = mid + 1;
			ans = mid;
		}
		else{
			r = mid - 1;
		}
	}
	cout << ((ans >= 1) ? ans : -1) ;
	
	return 0;
}

• Subtask 1: 69 / 100