Submission #110762

#	Time	Username	Problem	Language	Result	Execution time	Memory
110762		Mahdi_Jfri	007 (CEOI14_007)	C++14	100 / 100	403 ms	19556 KiB

007

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

#define ll long long
#define pb push_back

const int maxn = 2e5 + 20;

vector<int> adj[maxn];

int d[3][maxn] , x[maxn];

void bfs(int src , int k)
{
	memset(d[k] , 63  , sizeof d[k]);
	queue<int> q;
	q.push(src);
	d[k][src] = 0;

	while(!q.empty())
	{
		int v = q.front();
		q.pop();
		for(auto u : adj[v])
			if(d[k][u] > d[k][v] + 1)
			{
				d[k][u] = d[k][v] + 1;
				q.push(u);
			}
	}
}

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

	int n , m;
	cin >> n >> m;

	int a , b , s , t;

	cin >> s >> t >> a >> b;
	s-- , t-- , a-- , b--;

	for(int i = 0; i < m; i++)
	{
		int a , b;
		cin >> a >> b;
		a-- , b--;

		adj[a].pb(b);
		adj[b].pb(a);
	}

	bfs(a , 0) , bfs(b , 1) , bfs(t , 2);

	if(d[0][s] > d[0][t] || d[1][s] > d[1][t])
		return cout << -1 << endl , 0;

	vector<pair<int , int> > tmp;
	for(int i = 0; i < n; i++)
		tmp.pb({d[0][i] , i});

	sort(tmp.begin() , tmp.end());

	memset(x , -1 , sizeof x);
	for(auto sht : tmp)
	{
		int v = sht.second;

		x[v] = 0;
		for(auto u : adj[v])
			if(d[0][u] + 1 == d[0][v] && d[1][u] + 1 == d[1][v])
				x[v] = max(x[v] , x[u] + 1);
	}

	int res = 1e9;
	for(int t = 0; t < n; t++)
	{
		if(d[0][s] > d[0][t] || d[1][s] > d[1][t])
			res = min(res , d[2][t]);
		else if(d[0][s] == d[0][t] && d[1][s] == d[1][t] && x[t] > x[s])
			res = min(res , d[2][t]);
	}

	cout << res - 1 << endl;
}

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