Submission #1001250

#	Time	Username	Problem	Language	Result	Execution time	Memory
1001250		vjudge3	Tracks in the Snow (BOI13_tracks)	C++17	100 / 100	1662 ms	169620 KiB

tracks

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

bitset<4005> vis[4005], occ[4005], fox[4005];
vector<pair<int, int>> cur;
int h, w, dep = 1;
const int dr[4] = {0, 1, 0, -1}, dc[4] = {1, 0, -1, 0};

void bfs (int rt, int ct, bool f) {
	queue<pair<int, int>> q;
	q.push({rt, ct});
	while (!q.empty()) {
		auto [r, c] = q.front();
		q.pop();
		for (int k = 0; k < 4; k++) {
			int rv = r + dr[k], cv = c + dc[k];
			if (rv >= 1 && rv <= h && cv >= 1 && cv <= w && !vis[rv][cv] && occ[rv][cv] && fox[rv][cv] == f) {
				q.push({rv, cv});
				cur.push_back({rv, cv});
				vis[rv][cv] = true;
			}
		}
	}
}

int main () {
	cin >> h >> w;
	for (int i = 1; i <= h; i++) for (int j = 1; j <= w; j++) {
		char ch;
		cin >> ch;
		if (ch != '.') occ[i][j] = true;
		if (ch == 'F') fox[i][j] = true;
	}
	bfs(1, 1, fox[1][1]);
	while (true) {
		vector<pair<int, int>> last;
		last.swap(cur);
		for (auto& [r, c] : last) bfs(r, c, (dep & 1) ^ fox[1][1]);
		last.clear();
		if (cur.empty()) {
			cout << dep << '\n';
			return 0;
		}
		dep++;
	}
	return 0;
}

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