Submission #738687

#	Time	Username	Problem	Language	Result	Execution time	Memory
738687		airths	Tracks in the Snow (BOI13_tracks)	C++17	50.10 / 100	2106 ms	1048576 KiB

tracks

/*
 * 
 * 	^v^
 * 
 */
#include <iostream>
#include <string>
#include <cmath>
#include <vector>
#include <iomanip>
#include <map>
#include <numeric>
#include <functional>
#include <algorithm>
#include <set>
#include <queue>
#include <climits>
#include <cstdlib>
#include <chrono>
// #include <ext/pb_ds/assoc_container.hpp>
// #include <ext/pb_ds/tree_policy.hpp>
// using namespace __gnu_pbds;
using namespace std;
// #define ordered_set tree<ll, null_type, less<ll>, rb_tree_tag, tree_order_statistics_node_update>
#define iamtefu ios_base::sync_with_stdio(false); cin.tie(0);
#define ll int
#define ld long double
#define sc(a) scanf("%lld", &a);
#define scv(a, n) vector<ll> a(n);fl(i,0,n){sc(a[i])}
#define prl(a) fl(i,0,a.size()){printf("%lld ", a[i]);}printf("\n");
#define fl(i,a,n) for (ll i(a); i<n; i++)
#define rfl(i,a,n) for (ll i(n-1); i>=a; i--)
#define print(a) for (auto x:a){cout<<x<<" ";} cout<<"\n";
#define tt int tt; cin>>tt; for(;tt--;)
ll gcd(ll a, ll b){
	if (b==0){
		return a;
	}
	return gcd(b, a%b);
}
ll pw(ll a, ll b, ll m){
	ll res=1;
	a%=m;
	while (b){
		if (b&1){
			res=(res*a)%m;
		}
		a=(a*a)%m;
		b/=2;
	}
	return res;
}
void scn(){
	ll n, m; cin>>n>>m;
	vector <string> a(n+1);
	fl(i,0,n){
		cin>>a[i];
	}
	vector <ll> di={1, 1, 0, -1, -1, -1, 0, 1};
	vector <ll> dj={0, 1, 1, 1, 0, -1, -1, -1};
	vector <vector <ll>> vis(n, vector <ll>(m));
	ll cur = 0;
	function <void(ll, ll, char)> dfs=[&](ll i, ll j, char c){
		if (i<0 || i>=n || j<0 || j>=m || vis[i][j] || c!=a[i][j]){
			return;
		}
		vis[i][j]=cur;
		for (int d=0; d<8; d+=2){
			dfs(i+di[d], j+dj[d], c);
		}
	};
	fl(i,0,n){
		fl(j,0,m){
			if (a[i][j]!='.' && !vis[i][j]){
				cur++;
				dfs(i, j, a[i][j]);
			}
		}
	}
	vector <set <ll>> ed(cur+2);
	fl(i,0,n){
		fl(j,0,n){
			if (vis[i][j]==0){
				continue;
			}
			for (int d=0; d<8; d+=2){
				ll i1 = di[d]+i, j1 = dj[d]+j;
				if (i1>=0 && i1<n && j1>=0 && j1<m && vis[i1][j1]!=vis[i][j] && vis[i1][j1]!=0){
					ed[vis[i1][j1]].insert(vis[i][j]);
					ed[vis[i][j]].insert(vis[i1][j1]);
				}
			}
		}
	}
	vector <ll> ds(cur+2);
	queue <int> q;
	ds[1] = 0;
	q.push(1);
	// for (auto x:vis){
	// 	print(x)
	// }
	ll ans = 0;
	vector <ll> vs(cur+2);
	while (!q.empty()){
		auto j = q.front();
		q.pop();
		for (auto x:ed[j]){
			if (!vs[x]){
				ds[x] = ds[j]+1;
				vs[j]++;
				q.push(x);
			}
		}
	}
	ans = *max_element(ds.begin(), ds.end());
	cout<<ans+1<<'\n';
	// not necessarily distinct
}
int main(){
	iamtefu;
#if defined(airths)
	auto t1=chrono::high_resolution_clock::now();
	freopen("input.txt", "r", stdin);
	freopen("output.txt", "w", stdout);
#else
	//
#endif
	// tt
	{
		scn();
	}
#if defined(airths)
	auto t2=chrono::high_resolution_clock::now();
	ld ti=chrono::duration_cast<chrono::nanoseconds>(t2-t1).count();
	ti*=1e-6;
	cerr<<"Time: "<<setprecision(12)<<ti;
	cerr<<"ms\n";
#endif
	return 0;
}

• Subtask 1: 21.666666666666668 / 30
• Subtask 2: 28.4375 / 70