Submission #1123281

#	Time	Username	Problem	Language	Result	Execution time	Memory
1123281		lucaskojima	Tracks in the Snow (BOI13_tracks)	C++20	19.79 / 100	984 ms	121860 KiB

tracks

#include <bits/stdc++.h>
#define ff first
#define ss second
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define sz(x) (int)(x).size()

using namespace std;
using ll = long long;
using pii = pair<int, int>;

const char nl = '\n';
const ll LINF = 0x3f3f3f3f3f3f3f3f;
const int INF = 0x3f3f3f3f;

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

	int n, m; cin >> n >> m;

	vector<vector<char>> ma(n + 1, vector<char>(m + 1));
	for (int i = 1; i <= n; i++) {
		string s; cin >> s; s = '0' + s;
		for (int j = 1; j <= m; j++)
			ma[i][j] = s[j];
	}

	vector<vector<int>> dist(n + 1, vector<int>(m + 1, INF));
	deque<pii> q;

	q.push_front({1, 1});
	dist[1][1] = 1;

	auto val = [&](int x, int y) -> bool {
		return 1 <= x && x <= n && 1 <= y && y <= m;
	};

	vector<int> dx = {-1, 1, 0, 0};
	vector<int> dy = {0, 0, -1, 1};

	while (!q.empty()) {
		auto [x, y] = q.front(); q.pop_front();
		for (int d = 0; d < 4; d++) {
			int nx = x + dx[d];
			int ny = y + dy[d];
			if (!val(nx, ny)) continue;
			
			int w = (ma[x][y] == ma[nx][ny] ? 0 : 1);
			if (dist[x][y] + w < dist[nx][ny]) {
				dist[nx][ny] = dist[x][y] + w;
				if (w == 0)
					q.push_front({nx, ny});
				else
					q.push_back({nx, ny});
			}
		}
	}

	int ans = 0;
	for (int i = 1; i <= n; i++)
		for (int j = 1; j <= m; j++)
			if (dist[i][j] != INF)
				ans = max(ans, dist[i][j]);
	cout << ans << nl;
	return 0;
}

• Subtask 1: 6.6667 / 30
• Subtask 2: 13.125 / 70