Submission #843154

#	Time	Username	Problem	Language	Result	Execution time	Memory
843154		Mizo_Compiler	Tracks in the Snow (BOI13_tracks)	C++14	97.81 / 100	832 ms	1048576 KiB

tracks

#include <bits/stdc++.h>
using namespace std;
#pragma GCC optimize ("trapv")
typedef long long ll;
typedef double ld;
#define pb push_back
#define sz(x) int(x.size())
#define all(x) x.begin(),x.end()
#define F first
#define S second
const int N = 4000;
int n, m, ans = 1;
char c[N][N];
bool fc[N][N];
int dx[] = {1, -1, 0, 0};
int dy[] = {0, 0, 1, -1};
vector<pair<int, int>> f, r;
bool vis[N][N];

void dfs(int i, int j) {
	fc[i][j] = true;
	vis[i][j] = true;
	for (int ii = 0; ii < 4; ii++) {
		int nx = i + dx[ii], ny = j + dy[ii];
		if (nx < 0 || ny < 0 || nx >= n || ny >= m)continue;
		if (c[nx][ny] == c[0][0]) {
			if (!fc[nx][ny])dfs(nx, ny);
		} else if (!vis[nx][ny]) {
			if (c[nx][ny] == 'F')f.pb({nx, ny});
			else if (c[nx][ny] == 'R')r.pb({nx, ny});
			vis[nx][ny] = true;
		}
	}
}

int main () {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	cin >> n >> m;
	for (int i = 0; i < n; i++) {
		for (int j = 0; j < m; j++) {
			cin >> c[i][j];
		}
	}
	dfs(0, 0);
	char cur = 'R';
	if (c[0][0] == cur)cur = 'F';
	while (!f.empty() || !r.empty()) {
		if (cur == 'R') {
			if (!r.empty())ans++;
			while (!r.empty()) {
				int x = r.back().F, y = r.back().S;
				r.pop_back();
				for (int i = 0; i < 4; i++) {
					int nx = x + dx[i], ny = y + dy[i];
					if (nx < 0 || ny < 0 || nx >= n || ny >= m)continue;
					if (vis[nx][ny])continue;
					vis[nx][ny] = true;
					if (c[nx][ny] == 'R')r.pb({nx, ny});
					else if (c[nx][ny] == 'F')f.pb({nx, ny});
				}
			}
		} else {
			if (!f.empty()) {
				ans++;
			}
			while (!f.empty()) {
				int x = f.back().F, y = f.back().S;
				f.pop_back();
				for (int i = 0; i < 4; i++) {
					int nx = x + dx[i], ny = y + dy[i];
					if (nx < 0 || ny < 0 || nx >= n || ny >= m)continue;
					if (vis[nx][ny])continue;
					vis[nx][ny] = true;
					if (c[nx][ny] == 'R')r.pb({nx, ny});
					else if (c[nx][ny] == 'F')f.pb({nx, ny});
				}
			}
		}
		if (cur == 'F')cur = 'R';
		else cur = 'F';
	}
	cout << ans;
}

• Subtask 1: 30 / 30
• Subtask 2: 67.8125 / 70