Submission #1095584

#	Time	Username	Problem	Language	Result	Execution time	Memory
1095584		mat_jur	Tracks in the Snow (BOI13_tracks)	C++17	4.38 / 100	569 ms	210576 KiB

tracks

#include <bits/stdc++.h>
using namespace std;
#ifdef DEBUG
auto&operator<<(auto &o, pair<auto, auto> p) {o << "(" << p.first << ", " << p.second << ")"; return o;}
auto operator<<(auto&o,auto x)->decltype(x.end(),o){o<<"{"; for(auto e : x) o<<e<<", "; return o<<"}";}
#define debug(X) cerr << "["#X"]: " << X << '\n';
#else 
#define cerr if(0)cout
#define debug(X) ;
#endif
using ll = long long;
#define all(v) (v).begin(), (v).end()
#define ssize(x) int(x.size())
#define fi first
#define se second
#define mp make_pair
#define eb emplace_back

const int inf = 1e9;

int bfs(vector<vector<char>> c) {
	int n = ssize(c), m = ssize(c[0]);

	int dx[] = {0, 1, 0, -1}, dy[] = {1, 0, -1, 0};

	vector<vector<int>> dist {
		n,
		vector<int>(m, inf)
	};
	deque<pair<int, int>> q;

	for (int i = 0; i < n; ++i)
		for (int j = 0; j < m; ++j)
			if (c[i][j] == '.') {
				q.push_back({i, j});
				dist[i][j] = 0;
			}


	while (ssize(q)) {
		auto [x, y] = q.front();
		q.pop_front();

		for (int i = 0; i < 4; ++i) {
			if (!(x + dx[i] >= 0 && x + dx[i] < n && y + dy[i] >= 0 && y+dy[i] < m) || dist[x+dx[i]][y+dy[i]] != inf) continue;
			if (c[x][y] != c[x+dx[i]][y+dy[i]]) {
				dist[x+dx[i]][y+dy[i]] = dist[x][y] + 1;
				q.push_back({x+dx[i], y+dy[i]});
			}
			else {
				dist[x+dx[i]][y+dy[i]] = dist[x][y];
				q.push_front({x+dx[i], y+dy[i]});
			}
		}
	}

	int mx = -inf;
	for (int i = 1; i < n-1; ++i)
		for (int j = 1; j < m-1; ++j) 
			mx = max(mx, dist[i][j]);

	return mx;
}

int main() {
	ios_base::sync_with_stdio(false); cin.tie(nullptr);

	int h, w;
	cin >> h >> w;
	vector<vector<char>> c {
		h+2,
		vector<char>(w+2, '.')
	};

	for (int i = 1; i <= h; ++i)
		for (int j = 1; j <= w; ++j) 
			cin >> c[i][j];

	cout << bfs(c) << '\n';

	return 0;
}

Compilation message (stderr)

tracks.cpp: In function 'int bfs(std::vector<std::vector<char> >)':
tracks.cpp:27:3: warning: narrowing conversion of 'n' from 'int' to 'std::vector<std::vector<int> >::size_type' {aka 'long unsigned int'} [-Wnarrowing]
   27 |   n,
      |   ^
tracks.cpp: In function 'int main()':
tracks.cpp:71:4: warning: narrowing conversion of '(h + 2)' from 'int' to 'std::vector<std::vector<char> >::size_type' {aka 'long unsigned int'} [-Wnarrowing]
   71 |   h+2,
      |   ~^~

• Subtask 1: 0 / 30
• Subtask 2: 4.375 / 70