Submission #471457

#	Time	Username	Problem	Language	Result	Execution time	Memory
471457		huukhang	Tracks in the Snow (BOI13_tracks)	C++11	100 / 100	814 ms	126332 KiB

tracks

/*
						   Khangnh's code

"You can either experience the pain of discipline or the pain of regret. 
						The choice is yours."
*/

// - Only when necessary :d
// #pragma GCC optimize("Ofast")
// #pragma GCC optimize("unroll-loops")
// #pragma GCC target("avx,avx2,fma")

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

#define fileopen(a, b) freopen(((string)a + ".inp").c_str(), "r", stdin); freopen(((string)b + ".out").c_str(), "w", stdout);

#define ll long long
// #define int long long
#define ld long double
#define fi first
#define se second
#define pb push_back
#define pf push_front
#define pob pop_back
#define pof pop_front
#define eb emplace_back
typedef pair<int, int> pii;

const ll mod = 1e9 + 7;
const ll inf = 0x3f3f3f3f;
const double pi = acos(-1);
const double eps = 1e-9;

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

int n, m;
char a[4005][4005];
int d[4005][4005];
int ans = 0;

bool inside(int x, int y) {
	if (x < 1 || x > n || y < 1 || y > m) return false;
	return true;
}

void bfs(pii s) {
	for (int i = 1; i <= n; ++i)
		for (int j = 1; j <= m; ++j)
			d[i][j] = inf;

	deque<pii> dq;
	dq.pf(s);
	d[s.fi][s.se] = 1;

	while (!dq.empty()) {
		int x = dq.front().fi, y = dq.front().se;
		dq.pof();
		ans = max(ans, d[x][y]);

		for (int i = 0; i < 4; ++i) {
			int nx = x + dx[i], ny = y + dy[i];
			if (!inside(nx, ny)) continue;
			if (a[nx][ny] == '.') continue;

			bool w = a[x][y] != a[nx][ny];
			if (d[x][y] + w < d[nx][ny]) {
				d[nx][ny] = d[x][y] + w;
				(w ? dq.pb({nx, ny}) : dq.pf({nx, ny}));
			}
		}
	}
}

void solve() {
	cin >> n >> m;
	for (int i = 1; i <= n; ++i)
		for (int j = 1; j <= m; ++j)
			cin >> a[i][j];

	bfs({1, 1});
	cout << ans;
}

signed main() {
	#ifdef LOCAL
		fileopen("input", "output");
		auto start = clock();
	#endif
	#ifndef LOCAL
//		fileopen("LAH", "LAH");
	#endif
	ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
	int test = 1;
//	cin >> test;
	for (int tc = 1; tc <= test; ++tc) solve();
	#ifdef LOCAL
		auto end = clock();
		cout << "\n\nExecution time : " << double(end - start)/CLOCKS_PER_SEC << "[s]";
	#endif
	return 0;
}

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