Submission #37163

#	Time	Username	Problem	Language	Result	Execution time	Memory
37163		cheater2k	007 (CEOI14_007)	C++14	100 / 100	339 ms	18956 KiB

007

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

const int N = 200005;

int n, m, s, d, a, b;
vector<int> G[N];
int fa[N], fb[N];

void bfs(int start, int f[]) {
	for (int i = 1; i <= n; ++i) f[i] = -1;
	f[start] = 0;
	queue <int> q; q.push(start);

	while(!q.empty()) {
		int u = q.front(); q.pop();
		for (int v : G[u]) if (f[v] == -1) {
			f[v] = f[u] + 1; q.push(v);
		}
	}
}

int maxdep(int start) {
	vector<int> d(n + 1, -1);
	queue <int> q; q.push(start); d[start] = 0;
	int ans = 0;
	while(!q.empty()) {
		int u = q.front(); q.pop();
		ans = max(ans, d[u]);
		for (int v : G[u]) if (fa[v] == fa[u] - 1 && fb[v] == fb[u] - 1 && d[v] == -1) {
			d[v] = d[u] + 1; q.push(v);
		}
	}
	return ans;
}

int main() {
	ios_base::sync_with_stdio(false); cin.tie(0);
	cin >> n >> m;
	cin >> s >> d >> a >> b;
	while(m--) {
		int u, v; cin >> u >> v;
		G[u].push_back(v); G[v].push_back(u);
	}
	bfs(a, fa);
	bfs(b, fb);
	int wa = fa[d] - fa[s];
	int wb = fb[d] - fb[s];
	if (wa != wb) {
		printf("%d\n", max(min(wa, wb), -1));
	} else {
		int maxs = maxdep(s), maxd = maxdep(d);
		printf("%d\n", max(wa - (wa + maxs < maxd), -1));
	}
}

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