Submission #767689

#	Time	Username	Problem	Language	Result	Execution time	Memory
767689		lukehsiao	Tracks in the Snow (BOI13_tracks)	C++14	0 / 100	1309 ms	1048576 KiB

tracks

#include <bits/stdc++.h>
using namespace std;

const int mxN = 4000;

int H, W, id[mxN][mxN];
char grid[mxN][mxN];
bool vis[mxN][mxN];

int dx[4]{1, -1, 0, 0}, dy[4]{0, 0, 1, -1};

vector<int> dist;
queue<pair<int, int>> q;

void ff(int r, int c, int x) {
	id[r][c] = x;
	
	for (int i=0; i<4; ++i) {
		int nr = r + dx[i], nc = c + dy[i];
		if (nr >= 0 && nr < H && nc >= 0 && nc < W &&
				grid[nr][nc] == grid[r][c] && !id[nr][nc]) {
			ff(nr, nc, x);
		}
	}
}

void ff2(int r, int c) {
	vis[r][c] = true;

	for (int i=0; i<4; ++i) {
		int nr = r + dx[i], nc = c + dy[i];
		if (nr >= 0 && nr < H && nc >= 0 && nc < W &&
				!vis[nr][nc] && grid[nr][nc] != '.') {
			if (grid[nr][nc] != grid[r][c]) {
				if (dist[id[nr][nc]] == 2e9) {
					dist[id[nr][nc]] = dist[id[r][c]] + 1;
					q.push({nr, nc});
				}
			} else {
				ff2(nr, nc);
			}
		}
	}
}

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

	cin >> H >> W;
	for (int i=0; i<H; ++i)
		for (int j=0; j<W; ++j)
			cin >> grid[i][j];
	
	int cur = 0;
	for (int i=0; i<H; ++i) {
		for (int j=0; j<W; ++j) {
			if (!id[i][j] && grid[i][j] != '.')
				ff(i, j, ++cur);
		}
	}

	dist.resize(cur+1, 2e9);

	queue<pair<int, int>> q;
	q.push({0, 0});
	dist[1] = 0;

	while (!q.empty()) {
		int r = q.front().first;
		int c = q.front().second;
		q.pop();
		ff2(r, c);
	}

	int ans = 0;
	for (int i=1; i<=cur; ++i)
		ans = max(ans, dist[i]);
	
	cout << ans + 1 << '\n';
}

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