Submission #413617

#TimeUsernameProblemLanguageResultExecution timeMemory
413617sinamhdv007 (CEOI14_007)C++11
93 / 100
271 ms17676 KiB
#include <bits/stdc++.h> using namespace std; typedef long long ll; typedef pair<int, int> pii; typedef pair<ll, ll> pll; const int mod = 1000 * 1000 * 1000 + 7; const int INF = 1e9 + 100; const ll LINF = 1e18 + 100; #ifdef DEBUG #define dbg(x) cout << #x << " = " << (x) << endl << flush; #define dbgr(s, f) { cout << #s << ": "; for (auto _ = (s); _ != (f); _++) cout << *_ << ' '; cout << endl << flush; } #else #define dbg(x) ; #define dbgr(s, f) ; #endif #define FOR(i, a, b) for (int i = (a); i < (b); i++) #define fast_io ios::sync_with_stdio(false); cin.tie(0); cout.tie(0); #define all(x) (x).begin(), (x).end() #define pb push_back #define mp make_pair #define fr first #define sc second #define endl '\n' #define MAXN 200100 #define MAXE 600100 int n, m; int s, d, a, b; vector<int> adj[MAXN]; int h[3][MAXN]; bool mark[MAXN]; bool amark[2][MAXN], bmark[2][MAXN]; int ans; void bfs(pii r, int *h) { memset(mark, 0, sizeof(mark)); queue<int> q; if (r.fr >= 0) mark[r.fr] = true, q.push(r.fr); if (r.sc >= 0) mark[r.sc] = true, q.push(r.sc); while (!q.empty()) { int v = q.front(); q.pop(); for (int u : adj[v]) { if (mark[u]) continue; mark[u] = true; h[u] = h[v] + 1; q.push(u); } } } void findpars(int r, int *h, bool *mark) { queue<int> q; q.push(r); mark[r] = true; while (!q.empty()) { int v = q.front(); q.pop(); for (int u : adj[v]) { if (mark[u] || h[u] >= h[v]) continue; mark[u] = true; q.push(u); } } } int32_t main(void) { fast_io; cin >> n >> m; cin >> s >> d >> a >> b; FOR(i, 0, m) { int x, y; cin >> x >> y; adj[x].pb(y); adj[y].pb(x); } bfs({a, b}, h[0]); bfs({a, -1}, h[1]); bfs({b, -1}, h[2]); if (h[1][s] > h[1][d] || h[2][s] > h[2][d]) return cout << "-1\n", 0; ans = min(h[1][d] - h[1][s], h[2][d] - h[2][s]); // if (h[1][s] < h[1][d] || h[2][s] < h[2][d] || h[1][s] != h[2][s]) return cout << ans << endl, 0; findpars(s, h[1], amark[0]); findpars(s, h[2], bmark[0]); findpars(d, h[1], amark[1]); findpars(d, h[2], bmark[1]); int spy = h[0][s], doct = h[1][s]; FOR(i, 1, n + 1) { if (amark[0][i] && bmark[0][i]) spy = min(spy, h[0][i]); if (amark[1][i] && bmark[1][i]) doct = min(doct, h[0][i]); } if (spy > doct) ans--; cout << ans << endl; return 0; }
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