Submission #916915

#	Time	Username	Problem	Language	Result	Execution time	Memory
916915		OAleksa	Valley (BOI19_valley)	C++14	100 / 100	198 ms	52160 KiB

valley

#include <bits/stdc++.h>
//ako ovaj vaso daso misli da me pobedjuje.....
using namespace std;
#define int long long
#define f first
#define s second
const int N	= 1e5 + 69;
const int K = 18;
const int inf = 1e18;
int up[N][K];
int gas[N][K];
int n, s, q, e, cnt[N], dep[N], par[N], mn[N];
int tin[N], tout[N], timer, d[N];
vector<pair<int, int>> g[N];
vector<pair<int, int>> edges;
bool anc(int a, int b) {
	return tin[a] <= tin[b] && tout[a] >= tout[b];
}
int Lca(int a, int b) {
	if (anc(a, b))
		return a;
	else if (anc(b, a))
		return b;
	for (int i = K - 1;i >= 0;i--) {
		if (!anc(up[a][i], b) && up[a][i] > 0)
			a = up[a][i];
	}
	return up[a][0];
}
int distance(int a, int b) {
	return dep[a] + dep[b] - 2 * dep[Lca(a, b)];
}
void dfs(int v, int p) {
	tin[v] = ++timer;
	par[v] = p;
	up[v][0] = p;
	d[v] = d[p] + 1;
	if (cnt[v])
		mn[v] = 0;
	for (int i = 1;i < K;i++)
		up[v][i] = up[up[v][i - 1]][i - 1];
	for (auto u : g[v]) {
		if (u.f == p)
			continue;
		dep[u.f] = dep[v] + u.s;
		dfs(u.f, v);
		mn[v] = min(mn[v], mn[u.f] + u.s);
	}
	tout[v] = timer;
}
void dfs1(int v, int p) {
	gas[v][0] = min(mn[v] - dep[v], mn[p] - dep[p]);
	for (int i = 1;i < K;i++) 
		gas[v][i] = min(gas[v][i - 1], gas[up[v][i - 1]][i - 1]);
	for (auto u : g[v]) {
		if (u.f == p)
			continue;
		dfs1(u.f, v);
	}
}
signed main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  int tt = 1;
  //cin >> tt;
  while (tt--) {
  	cin >> n >> s >> q >> e;
  	for (int i = 0;i <= n;i++)
  		mn[i] = inf;
  	for (int i = 1;i <= n - 1;i++) {
  		int a, b, w;
  		cin >> a >> b >> w;
  		g[a].push_back({b, w});
  		g[b].push_back({a, w});
  		edges.push_back({a, b});
  	}
  	for (int i = 1;i <= s;i++) {
  		int x;
  		cin >> x;
  		cnt[x] = 1;
  	}
  	dfs(e, 0);
  	dfs1(e, 0);
  	for (int j = 0;j < q;j++) {
  		int i, st;
  		cin >> i >> st;
  		--i;
  		int a, b;
  		tie(a, b) = edges[i];
  		if (dep[a] < dep[b])
  			swap(a, b);	
  		int ans = inf;
  		if (s == n) {
  			if (!anc(a, st) || !anc(b, st)) 
  				ans = -1;
  			else
  				ans = 0;
  		}
  		else {
  			if (!anc(a, st) || !anc(b, st)) 
  				ans = -1;
  			else {
  				int t = st;
  				int dist = d[st] - d[a];
  				ans = mn[st];
  				for (int i = 0;i < K;i++) {
  					if (dist & (1 << i)) {
  						ans = min(ans, gas[t][i] + dep[st]);
  						t = up[t][i];						
  					}
  				}
  			}
  		}
  		if (ans == inf)
  			cout << "oo\n";
  		else if (ans == -1)
  			cout << "escaped\n";
  		else
  			cout << ans << '\n';
  	}
	}
  return 0;
}

• Subtask 1: 9 / 9
• Subtask 2: 27 / 27
• Subtask 3: 23 / 23
• Subtask 4: 41 / 41