Submission #1198437

#	Time	Username	Problem	Language	Result	Execution time	Memory
1198437		aguss	Highway Tolls (IOI18_highway)	C++20	0 / 100	253 ms	327680 KiB

highway

#include "highway.h"
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define dbg(x) cerr << #x << ": " << x << "\n";
vector<pair<int, int>> depth, path;
vector<vector<pair<int, int>>> arr;
void dfs(int node, int prev = -1){
	for(const auto &i : arr[node]){
		if(i.first == prev) continue;
		path.push_back({i.first, i.second});
		depth[i.first] = {depth[node].first + 1, i.second};
		dfs(i.first, node);
	}	
}
int max_depth(int a, int b){
	if(depth[a].first > depth[b].first) return a;
	return b;
}
int min_depth(int a, int b){
	if(depth[a].first < depth[b].first) return a;
	return b;
}

pair<int, int> solve(int dis2, int dis1, int A, int B){
	int x, y;
	y = (dis2 - dis1) / (B - A);
	x = dis1 / A - y;
	return {x, y};
}

void find_pair(int N, std::vector<int> U, std::vector<int> V, int A, int B) {
	depth.assign(N, {0, 0});
	arr.assign(N, vector<pair<int, int>>());
	vector<int> pos_ans;
	vector<int> vec(U.size(), 0);
	long long dis = ask(vec);
	for(int i = 0; i < (int)U.size(); i++){
		arr[U[i]].push_back({V[i], i});
		arr[V[i]].push_back({U[i], i});
	}
	pair<int, int> root;
	for(int i = 0; i < (int)arr.size(); i++){
		if(arr[i].size() == 1){
			root = {i, arr[i][0].second};
			break;
		}
	}
	dfs(root.first);
	int l = 0, r = U.size(), m;
	ll dis2 = 0;
	while(l + 1 < r){
		m = (l + r) / 2;
		vec.assign(U.size(), 0);
		for(int i = 0; i < m; i++)
			vec[path[i].second] = 1;
		dis2 = ask(vec);
		if(dis2 != dis){
			if(dis2 / B == dis / A){
				r = m;
				continue;
			}
			break;
		} 
		l = m;
	}
	// solve returns {x, y};
	// y --- m --- x
	m = (l + r) / 2;
	pair<int, int> dism = solve(dis2, dis, A, B);
	int mid = min_depth(U[path[m].second], V[path[m].second]), s = 0, t = 0;
	for(int i = 0; i < N; i++){
		if(depth[i].first == depth[mid].first - dism.second) s = i;
		if(depth[i].first == depth[mid].first + dism.first) t = i;
	}
	answer(s, t);
}

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