// partially_correct/sol_birka0_D1_2N.cpp
#include "longesttrip.h"
#include <random>
#include <algorithm>
using namespace std;
vector<int> longest_trip(int N, int /*D*/)
{
srand(time(0));
std::vector<int> ids(N);
for (int i = 0; i < N; i++)
ids[i] = i;
random_shuffle(ids.begin(), ids.end());
vector<int> t1 = {ids[0]}, t2 = {ids[1]};
for (int j = 2; j < N; ++j)
{
int i = ids[j];
if (t2.empty())
{
t2 = {i};
continue;
}
bool add1 = are_connected({t1.back()}, {i});
bool add2 = are_connected({t2.back()}, {i});
if (add1 && add2)
{
t1.push_back(i);
while (!t2.empty())
{
t1.push_back(t2.back());
t2.pop_back();
}
}
else if (add1)
{
t1.push_back(i);
}
else if (add2)
{
t2.push_back(i);
}
else
{
while (!t2.empty())
{
t1.push_back(t2.back());
t2.pop_back();
}
t2 = {i};
}
}
if (t2.size() > t1.size())
swap(t1, t2);
if (t2.empty() || !are_connected(t1, t2))
{
return t1;
}
if (are_connected({t1.back()}, {t2[0]}))
{
t1.insert(t1.end(), t2.begin(), t2.end());
return t1;
}
reverse(t2.begin(), t2.end());
if (are_connected({t1.back()}, {t2[0]}))
{
t1.insert(t1.end(), t2.begin(), t2.end());
return t1;
}
reverse(t1.begin(), t1.end());
if (are_connected({t1.back()}, {t2[0]}))
{
t1.insert(t1.end(), t2.begin(), t2.end());
return t1;
}
reverse(t2.begin(), t2.end());
if (are_connected({t1.back()}, {t2[0]}))
{
t1.insert(t1.end(), t2.begin(), t2.end());
return t1;
}
int lo = 0, hi = t2.size();
while (lo + 1 < hi)
{
int mid = (lo + hi) / 2;
if (are_connected(t1, vector<int>(t2.begin() + mid, t2.begin() + hi)))
{
lo = mid;
}
else
{
hi = mid;
}
}
int x = lo;
lo = 0, hi = t1.size();
while (lo + 1 < hi)
{
int mid = (lo + hi) / 2;
if (are_connected({t2[x]}, vector<int>(t1.begin() + mid, t1.begin() + hi)))
{
lo = mid;
}
else
{
hi = mid;
}
}
int y = lo;
vector<int> t(t1.begin() + y + 1, t1.end());
t.insert(t.end(), t1.begin(), t1.begin() + y + 1);
t.insert(t.end(), t2.begin() + x, t2.end());
t.insert(t.end(), t2.begin(), t2.begin() + x);
return t;
}
