Submission #97114

#	Time	Username	Problem	Language	Result	Execution time	Memory
97114		tincamatei	Highway Tolls (IOI18_highway)	C++14	100 / 100	324 ms	10892 KiB

highway

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

using namespace std;

const int MAX_N = 90000;
const int MAX_M = 130000;

struct Edge {
	int a, b;
	int other(int x) {
		return a ^ b ^ x;
	}
} edge[MAX_M];

vector<int> graph[MAX_N];
vector<pair<int, int> > tree[2];
bool viz[MAX_N];

void buildSmallTrees(int eid, const std::vector<int> &U,
                              const std::vector<int> &V) {
	int X, Y;
	for(int i = 0; i < U.size(); ++i) {
		edge[i] = {U[i], V[i]};

		graph[U[i]].push_back(i);
		graph[V[i]].push_back(i);
	}
	X = edge[eid].a, Y = edge[eid].b;

	deque<pair<int, int> > q;
	q.push_back(make_pair(X, 0));
	q.push_back(make_pair(Y, 1));
	tree[0].push_back(make_pair(X, eid));
	tree[1].push_back(make_pair(Y, eid));
	viz[X] = viz[Y] = true;


	while(!q.empty()) {
		int nod, t;
		nod = q.front().first;
		t = q.front().second;
		q.pop_front();
		
		for(auto it: graph[nod]) {
			int son = edge[it].other(nod);
			if(!viz[son]) {
				viz[son] = true;
				tree[t].push_back(make_pair(son, it));
				q.push_back(make_pair(son, t));
			}
		}
	}
}

int searchTree(int t, int M, long long refpath) {
	int st = -1, dr = tree[t].size();
	vector<int> w(M, 0);

	reverse(tree[t].begin(), tree[t].end());

	while(dr - st > 1) {
		int mid = (st + dr) / 2;
		for(int i = 0; i < M; ++i)
			w[i] = 1;
		for(int i = 0; i < 2; ++i)
			for(auto it: tree[i])
				w[it.second] = 0;
		for(int i = 0; i <= mid; ++i)
			w[tree[t][i].second] = 1;
		if(ask(w) > refpath)
			dr = mid;
		else
			st = mid;
	}
	return tree[t][dr].first;
}

void find_pair(int N, std::vector<int> U, std::vector<int> V, int A, int B) {
	int M = U.size();
	int st, dr;
	long long refPath;
	vector<int> w(M, 0);
	refPath = ask(w);

	st = -1, dr = M;
	while(dr - st > 1) {
		int mid = (st + dr) / 2;
		for(int i = 0; i <= mid; ++i)
			w[i] = 1;
		for(int i = mid + 1; i < M; ++i)
			w[i] = 0;

		if(ask(w) > refPath)
			dr = mid;
		else
			st = mid;
	}

	// Muchia (U[dr], V[dr]) face parte dintr-un drum sigur
	buildSmallTrees(dr, U, V);
	answer(searchTree(0, M, refPath), searchTree(1, M, refPath));
}

Compilation message (stderr)

highway.cpp: In function 'void buildSmallTrees(int, const std::vector<int>&, const std::vector<int>&)':
highway.cpp:23:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i = 0; i < U.size(); ++i) {
                 ~~^~~~~~~~~~

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