Submission #162957

#	Time	Username	Problem	Language	Result	Execution time	Memory
162957		Minnakhmetov	Highway Tolls (IOI18_highway)	C++14	100 / 100	366 ms	14532 KiB

highway

#include "highway.h"
#include <bits/stdc++.h>

using namespace std;

#define ll long long
#define all(aaa) aaa.begin(), aaa.end()

struct E {
	int to, i;
};

const int N = 2e5 + 5;
vector<E> g[N];
int anc[N], d[N], pr[N], h[N];

void find_pair(int n, vector<int> u, vector<int> v, int a, int b) {
	int m = u.size();

	for (int i = 0; i < m; i++) {
		g[u[i]].push_back({v[i], i});
		g[v[i]].push_back({u[i], i});
		pr[i] = rand();
	}

	ll dist = ask(vector<int>(m, 0)) / a;

	int l = -1, r = m - 1;
	while (r - l > 1) {
		int p = (l + r) >> 1;
		vector<int> w(m, 0);
		fill(w.begin(), w.begin() + p + 1, 1);
		if (ask(w) != dist * a)
			r = p;
		else
			l = p;
	}

	int rt[2] = {u[r], v[r]},
		mid = r;

	// cout << rt[0] << " " << rt[1] << "\n";

	queue<int> q;
	fill(d, d + n, -1);
	d[rt[0]] = d[rt[1]] = 0;
	h[rt[1]] = 1;
	q.push(rt[0]);
	q.push(rt[1]);

	vector<int> half[2];

	while (!q.empty()) {
		int node = q.front();
		q.pop();

		for (E e : g[node]) {
			if (d[e.to] == -1) {
				d[e.to] = d[node] + 1;
				h[e.to] = h[node];
				anc[e.to] = e.i;
				half[h[node]].push_back(e.i);
				q.push(e.to);
			}
		}
	}

	for (int i = 0; i < m; i++) {
		if (d[u[i]] > d[v[i]])
			swap(u[i], v[i]);
	}


	for (int i = 0; i < 2; i++) {
		sort(all(half[i]), [&](int x, int y) {
			return d[v[x]] > d[v[y]];
		});
	}

	// for (int i = 0; i < 2; i++) {
	// 	for (int j : half[i]) {
	// 		cout << u[j] << " " << v[j] << "\n";
	// 	}
	// 	cout << "\n";
	// }

	int ans[2];

	for (int i = 0; i < 2; i++) {
		int l = -1, r = half[i].size();

		while (r - l > 1) {
			int p = (l + r) >> 1;
			vector<int> w(m, 1);

			w[mid] = 0;

			for (int j : half[i ^ 1])
				w[j] = 0;
			for (int j = p + 1; j < half[i].size(); j++) {
				w[half[i][j]] = 0;
			}

			if (ask(w) != dist * a)
				r = p;
			else
				l = p;
		}

		if (r == half[i].size())
			ans[i] = rt[i];
		else
			ans[i] = v[half[i][r]];
	}

	// cout << ans[0] << " " << ans[1] << "\n";

	answer(ans[0], ans[1]);
}

Compilation message (stderr)

highway.cpp: In function 'void find_pair(int, std::vector<int>, std::vector<int>, int, int)':
highway.cpp:100:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    for (int j = p + 1; j < half[i].size(); j++) {
                        ~~^~~~~~~~~~~~~~~~
highway.cpp:110:9: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   if (r == half[i].size())
       ~~^~~~~~~~~~~~~~~~~

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