Submission #69482

#	Time	Username	Problem	Language	Result	Execution time	Memory
69482		MatheusLealV	Tracks in the Snow (BOI13_tracks)	C++17	75.94 / 100	2141 ms	1049600 KiB

tracks

#include <bits/stdc++.h>
#define N 4003
#define f first
#define s second
using namespace std;
typedef pair<int, int> pii;

int n, m, ans, cnt, ok[N][N], dx[4] = {0, 0, 1, -1}, dy[4] = {1, -1, 0, 0};

int id[N][N], pai[N*N], dist[N*N];

char mat[N][N], T;

vector<int> grafo[N*N];

void dfs(int x, int y, int &p)
{
	//cout<<"DFS "<<x<<" "<<y<<"\n";
	ok[x][y] = 1;

	pai[id[x][y]] = p;

	for(int pp = 0; pp < 4; pp++)
	{
		int a = x + dx[pp], b = y + dy[pp];

		if(!a or !b or a > n or b > m or mat[a][b] != mat[x][y] or ok[a][b]) continue;

		//cout<<"VIZ "<<x<<" "<<y<<" "<<a<<" "<<b<<"\n";

		dfs(a, b, p);
	}
}

int main()
{
	//ios::sync_with_stdio(false); cin.tie(0);

	cin>>n>>m;

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

		 	id[i][j] = ++cnt;

		 	pai[id[i][j]] = id[i][j];
		}
	}

	for(int i = 1; i <= n; i++)
	{
		for(int j = 1; j <= m; j++)
		{
			if(mat[i][j] == '.' or ok[i][j]) continue;
			//cout<<"INI "<<i<<" "<<j<<"\n";
			dfs(i, j, id[i][j]);	
			//cout<<"FIM "<<i<<" "<<j<<"\n";
		}
	}

	for(int i = 1; i <= n; i++)
	{
		for(int j = 1; j <= m; j++)
		{
			if(mat[i][j] == '.') continue;

			for(int p = 0; p < 4; p++)
			{
				int a = i + dx[p], b = j + dy[p];

				if(!a or !b or a > n or b > m) continue;

				if(mat[a][b] != mat[i][j] and mat[a][b] != '.')
				{
					int u = pai[id[a][b]], v = pai[id[i][j]];

					grafo[u].push_back(v);
				}
			}
		}
	}

	queue<int> fila;

	dist[pai[id[1][1]]] = 1;

	fila.push(pai[id[1][1]]);

	while(!fila.empty())
	{
		int x = fila.front();

		ans = max(ans, dist[x]);

		fila.pop();

		for(auto v: grafo[x])
		{
			if(dist[v] == 0)
			{
				dist[v] = dist[x] + 1;

				fila.push(v);
			}
		}
	}

	cout<<ans<<"\n";
}

• Subtask 1: 30 / 30
• Subtask 2: 45.9375 / 70