Submission #501399

#	Time	Username	Problem	Language	Result	Execution time	Memory
501399		sidon	Highway Tolls (IOI18_highway)	C++17	100 / 100	462 ms	11232 KiB

highway

#include <bits/stdc++.h>
#include "highway.h"
using namespace std;
using ll = long long;

void find_pair(int N, vector<int> U, vector<int> V, int A, int B) {
	int M = size(U), x = 0, u, d[2][N];
	vector<int> w(M);
	ll least = ask(w);

	for(int b = 1<<17; b/=2; ) if(x + b < M) {
		fill(begin(w), begin(w) + x + b, 1);
		bool ok = ask(w) == least;
		fill(begin(w), begin(w) + x + b, 0);
		if(ok) x |= b;
	}

	array<int, 2> S = {U[x], V[x]}, ans {};
	vector<array<int, 2>> g[N], a;

	for(int i = x; i < M; i++) {
		g[U[i]].push_back({V[i], i});
		g[V[i]].push_back({U[i], i});
	}

	for(int k : {0, 1}) {
		fill(d[k], d[k] + N, N);
		queue<int> q;
		d[k][S[k]] = 0;
		q.push(S[k]);

		while(!empty(q)) {
			u = q.front(); q.pop();
			for(auto &[v, e] : g[u]) if(d[k][v] > d[k][u] + 1)
				d[k][v] = d[k][u] + 1, q.push(v);
		}
	}

	for(int k : {0, 1}) {
		a.clear();

		for(int i = 0; i < N; i++)
			if(d[k][i] < d[!k][i]) a.push_back({-d[k][i], i});

		sort(begin(a), end(a));

		for(int b = 1<<17; b/=2; ) if(ans[k] + b < size(a)) {
			fill(begin(w), begin(w) + x, 1);
			for(int i = ans[k] + b; --i >= 0; )
				for(auto &[v, e] : g[a[i][1]])
					w[e] = 1;
			bool ok = ask(w) == least;

			for(int i = ans[k] + b; --i >= 0; )
				for(auto &[v, e] : g[a[i][1]])
					w[e] = 0;
			fill(begin(w), begin(w) + x, 0);
			if(ok) ans[k] |= b;
		}
		ans[k] = a[ans[k]][1];
	}

	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:47:44: warning: comparison of integer expressions of different signedness: 'std::array<int, 2>::value_type' {aka 'int'} and 'std::vector<std::array<int, 2> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   47 |   for(int b = 1<<17; b/=2; ) if(ans[k] + b < size(a)) {

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