Submission #978896

#	Time	Username	Problem	Language	Result	Execution time	Memory
978896		happypotato	Highway Tolls (IOI18_highway)	C++17	18 / 100	220 ms	262144 KiB

highway

#include "highway.h"
#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define pii pair<int, int>
#define ff first
#define ss second
#define pb push_back
const int mxN = 1e5;
vector<pii> adj[mxN];
int par[mxN];
int paredge[mxN];
int depth[mxN];
void dfs1(int u = 0, int dep = 0, int pp = -1) {
	depth[u] = dep;
	for (pii v : adj[u]) {
		if (v.ff == pp) continue;
		paredge[v.ff] = v.ss;
		par[v.ff] = u;
		dfs1(v.ff, dep + 1, u);
	}
}
void find_pair(int n, vector<int> U, vector<int> V, int A, int B) {
	int m = U.size();
	vector<pair<pii, int>> edges(m);
	for (int i = 0; i < m; i++) {
		edges[i] = {{U[i], V[i]}, i};
		adj[U[i]].pb({V[i], i});
		adj[V[i]].pb({U[i], i});
	}
	vector<int> pass(m, 0);
	ll base = ask(pass);
	dfs1(); paredge[0] = -1;
	int S, T, LCA, ldep;
	// search for last element
	{
		vector<pii> v;
		for (int i = 1; i < n; i++) {
			v.pb({depth[i], i});
		}
		sort(v.begin(), v.end(), greater<pii>());
		int lb = 0, rb = (int)(v.size()) - 1;
		while (lb < rb) {
			int mid = (lb + rb + 1) >> 1;
			for (int i = 0; i < mid; i++) pass[paredge[v[i].ss]] = 1;
			ll ret = ask(pass);
			if (ret == base) lb = mid;
			else rb = mid - 1;
			for (int i = 0; i < mid; i++) pass[paredge[v[i].ss]] = 0;
		}
		S = v[lb].ss;
	}
	// search for depth of LCA
	{
		int lb = 0, rb = n;
		while (lb < rb) {
			int mid = (lb + rb + 1) >> 1;
			for (int i = 1; i < n; i++) {
				pass[paredge[i]] = (depth[i] <= mid);
			}
			ll ret = ask(pass);
			if (ret == base) lb = mid;
			else rb = mid - 1;
			for (int i = 0; i < n; i++) pass[i] = 0;
		}
		ldep = lb;
	}
	LCA = S;
	for (int i = depth[S]; i > ldep; i--) LCA = par[LCA];
	if (1LL * (depth[S] - ldep) * A == base) return answer(LCA, S);
	int rdep = (base / A) - (depth[S] - ldep) + ldep;
	int avoid = S;
	for (int i = depth[S]; i > rdep; i--) avoid = par[avoid];
	// search for remaining node
	{
		vector<int> v;
		for (int i = 0; i < n; i++) {
			if (depth[i] == rdep && i != avoid) v.pb(i);
		}
		int lb = 0, rb = (int)(v.size()) - 1;
		while (lb < rb) {
			int mid = (lb + rb) >> 1;
			for (int i = 0; i <= mid; i++) pass[paredge[v[i]]] = 1;
			ll ret = ask(pass);
			if (ret != base) rb = mid;
			else lb = mid + 1;
			for (int i = 0; i <= mid; i++) pass[paredge[v[i]]] = 0;
		}
		T = v[lb];
	}
	answer(S, T);
}

• Subtask 1: 5 / 5
• Subtask 2: 7 / 7
• Subtask 3: 6 / 6
• Subtask 4: 0 / 33
• Subtask 5: 0 / 18
• Subtask 6: 0 / 31