Submission #103675

#	Time	Username	Problem	Language	Result	Execution time	Memory
103675		tugushka	Mecho (IOI09_mecho)	C++14	57 / 100	315 ms	66560 KiB

mecho

#include<bits/stdc++.h>
#define mp make_pair
#define pb push_back
using namespace std;

using pii = pair < int, int >;
const int N = 805;
const int dx[] = {1, -1, 0, 0}, dy[] = {0, 0, 1, -1};

char a[N][N];
pii mecho, home;
int n, s, hive[N][N];
bool used[N][N];

void hive_bfs(){
	memset( hive, 11, sizeof(hive) );
	queue < pii > q;
	for(int i = 0 ; i < n ; i++) for(int j = 0 ; j < n ; j++){
		if( a[i][j] == 'H' ){
			q.push( mp( i, j ) );
			hive[i][j] = 0;
		}
	}

	int dis = 0;
	while( !q.empty() ){
		dis += s;
		int sz = q.size();
		while( sz-- ){
			int x, y;
			tie(x, y) = q.front();
			q.pop();
			for(int i = 0 ; i < 4 ; i++){
				int tx = x+dx[i], ty = y+dy[i];
				if( tx < 0 || ty < 0 || tx >= n || ty >= n ) continue;
				if( a[tx][ty] == 'G' && hive[tx][ty] > 2e6 ){
					hive[tx][ty] = dis;
					q.push( mp( tx, ty ) );
				}
			}
		}
	}

	/*
	for(int i = 0 ; i < n ; i++){
		for(int j = 0 ; j < n ; j++){
			if( hive[i][j] > 2e6 ) printf("@@ ");
			else printf("%2d ", hive[i][j]);
		}
		printf("\n");
	}
	*/
}

bool mecho_bfs(int start_time){
	memset( used, 0, sizeof(used) );

	queue < pii > q;
	q.push( mecho );

	int dis = start_time;
	while( !q.empty() ){
		dis++;
		// cout << "dis " << dis << " : ";

		int sz = q.size();
		while( sz-- ){
			int x, y;
			tie(x, y) = q.front();
			q.pop();
			for(int i = 0 ; i < 4 ; i++){
				int tx = x+dx[i], ty = y+dy[i];
				if( tx < 0 || ty < 0 || tx >= n || ty >= n ) continue;
				if( !used[tx][ty] && a[tx][ty] == 'G' && hive[tx][ty] > dis ){
					used[tx][ty] = 1;
					// cout << "( " << tx << ',' << ty << " ), ";
					q.push( mp( tx, ty ) );
				}
			}
		}
		// cout << endl;
	}

	return used[ home.first ][ home.second ];
}

int main(){
	scanf("%d %d", &n, &s);
	for(int i = 0 ; i < n ; i++){
		scanf("%s", a[i]);
	}
	hive_bfs();
	for(int i = 0 ; i < n ; i++) for(int j = 0 ; j < n ; j++){
		if( a[i][j] == 'D' ){
			home = mp( i, j );
			a[i][j] = 'G';
		}
		if( a[i][j] == 'M' ){
			mecho = mp( i, j );
		}
	}

	if( !mecho_bfs( 0 ) ){
		printf("-1\n");
		return 0;
	}

	int l = 0, r = n*n, res;
	while( l <= r ){
		int mid = (l+r)/2;

		if( mecho_bfs( s*(mid) ) ){
			res = mid;
			l = mid+1;
		} else {
			r = mid-1;
		}
	}

	/*
	int res = 0;
	while( mecho_bfs( s*(res+1) ) ) res++;
	*/
	cout << res << endl;
}

Compilation message (stderr)

mecho.cpp: In function 'int main()':
mecho.cpp:88:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d %d", &n, &s);
  ~~~~~^~~~~~~~~~~~~~~~~
mecho.cpp:90:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%s", a[i]);
   ~~~~~^~~~~~~~~~~~
mecho.cpp:124:10: warning: 'res' may be used uninitialized in this function [-Wmaybe-uninitialized]
  cout << res << endl;
          ^~~

• Subtask 1: 57 / 100