Submission #101178

#	Time	Username	Problem	Language	Result	Execution time	Memory
101178		square1001	007 (CEOI14_007)	C++14	100 / 100	419 ms	17144 KiB

007

#include <queue>
#include <vector>
#include <iostream>
using namespace std;
const int inf = 1012345678;
vector<int> shortest_path(int src, vector<vector<int> > &G) {
	int N = G.size();
	vector<int> dist(N, inf);
	queue<int> que;
	que.push(src);
	dist[src] = 0;
	while (!que.empty()) {
		int u = que.front(); que.pop();
		for (int i : G[u]) {
			if (dist[i] == inf) {
				dist[i] = dist[u] + 1;
				que.push(i);
			}
		}
	}
	return dist;
}
int main() {
	cin.tie(0);
	ios_base::sync_with_stdio(false);
	int N, M;
	cin >> N >> M;
	int S, D, A, B;
	cin >> S >> D >> A >> B; --S, --D, --A, --B;
	vector<vector<int> > G(N);
	for (int i = 0; i < M; ++i) {
		int a, b;
		cin >> a >> b; --a, --b;
		G[a].push_back(b);
		G[b].push_back(a);
	}
	vector<int> da = shortest_path(A, G);
	vector<int> db = shortest_path(B, G);
	if (da[S] != db[S] || da[D] != db[D]) {
		int ans = min(da[D] - da[S], db[D] - db[S]);
		cout << (ans < 0 ? -1 : ans) << endl;
	}
	else {
		vector<int> ds = shortest_path(S, G);
		vector<int> dd = shortest_path(D, G);
		int mins = inf, mind = inf;
		for (int i = 0; i < N; ++i) {
			if (da[i] == db[i]) {
				if (da[i] + ds[i] == da[S]) mins = min(mins, da[i]);
				if (da[i] + dd[i] == da[D]) mind = min(mind, da[i]);
			}
		}
		int ans = da[D] - da[S] - (mins > mind ? 1 : 0);
		cout << (ans < 0 ? -1 : ans) << endl;
	}
	return 0;
}

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