Submission #1181621

#	Time	Username	Problem	Language	Result	Execution time	Memory
1181621		trvhung	Tracks in the Snow (BOI13_tracks)	C++20	100 / 100	579 ms	132856 KiB

tracks

#include <bits/stdc++.h>
// #include <ext/rope>
// #include <ext/pb_ds/assoc_container.hpp>

// using namespace __gnu_pbds;
// using namespace __gnu_cxx;
using namespace std;

// #define   ordered_set tree<int, null_type,less<int>, rb_tree_tag,tree_order_statistics_node_update>
#define            ll long long
#define           ull unsigned long long
#define            ld long double
#define            pb push_back
#define  bit(mask, i) ((mask >> i) & 1)
#define            el '\n'
#define             F first
#define             S second

template <class X, class Y> bool maximize(X &x, const Y &y) { return (x < y ? x = y, 1 : 0); }
template <class X, class Y> bool minimize(X &x, const Y &y) { return (x > y ? x = y, 1 : 0); }

const int INF = 1e9;
const ll LINF = 1e18;
const int MOD = 1e9 + 7;
const int MULTI = 0;
const ld eps = 1e-9;
const int dx[4] = {0, 1, 0, -1}, dy[4] = {1, 0, -1, 0}; // R D L U
const int ddx[4] = {-1, 1, 1, -1}, ddy[4] = {1, 1, -1, -1}; // UR DR DL UL
const char cx[4] = {'R', 'D', 'L', 'U'};
const ll base = 31;
const int nMOD = 2;
const ll mods[] = {(ll)1e9 + 10777, (ll)1e9 + 19777, (ll)1e9 + 3, (ll)1e9 + 3777};

const int maxn = 4e3 + 5;
int n, m, dist[maxn][maxn];
char c[maxn][maxn];
bool vis[maxn][maxn];

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

	deque<pair<int, int>> dq;
	dist[1][1] = 0; dq.push_back(make_pair(1, 1));

	while (!dq.empty()) {
		int x = dq.front().F, y = dq.front().S;
		dq.pop_front();

		if (vis[x][y]) continue;
		vis[x][y] = true;

		for (int i = 0; i < 4; ++i) {
			int nx = x + dx[i], ny = y + dy[i];
			if (nx < 1 || nx > n || ny < 1 || ny > m) continue;
			if (c[nx][ny] == '.') continue;
			int w = (c[x][y] != c[nx][ny]);
			if (minimize(dist[nx][ny], dist[x][y] + w)) {
				if (w)
					dq.push_back(make_pair(nx, ny));
				else 
					dq.push_front(make_pair(nx, ny));
			}
		}
	}

	int res = 0;
	for (int i = 1; i <= n; ++i)
		for (int j = 1; j <= m; ++j)
			if (c[i][j] != '.')
				maximize(res, dist[i][j]);

	cout << res + 1;
}

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

    if (!MULTI) solve();
    else {
        int test; cin >> test;
        while (test--) solve();
    }
    
    return 0;
}

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