Submission #501395

#	Time	Username	Problem	Language	Result	Execution time	Memory
501395		sidon	Highway Tolls (IOI18_highway)	C++17	6 / 100	132 ms	8800 KiB

highway

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

long long ask(const std::vector<int> &w);
void answer(int s, int t);

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

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

	array<int, 2> S = {U[x], V[x]}, ans {};
	vector<array<int, 2>> g[N];
	vector<int> ord[2], 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, 1e18);
		queue<int> q;
		d[k][S[k]] = 0;
		q.push(S[k]);

		while(!empty(q)) {
			ord[k].push_back(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 : ord[k])
			if(d[k][i] < d[!k][i]) a.push_back(i);

		for(int b = 1<<17; b/=2; ) if(ans[k] + b < size(a)) {
			vector<int> w(M);
			fill(begin(w), begin(w) + x, 1);

			for(int i = ans[k] + b; --i >= 0; )
				for(auto &[v, e] : g[a[size(a)-ans[k]-b]])
					w[e] = 1;

			if(ask(w) == least) ans[k] |= b;
		}
		ans[k] = a[size(a)-1-ans[k]];
	}

	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<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   47 |   for(int b = 1<<17; b/=2; ) if(ans[k] + b < size(a)) {

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