#include "longesttrip.h"
#include <bits/stdc++.h>
#define pb push_back
using namespace std;
void extend(vector<int>& a, vector<int>& b, int first, int last)
{
for (int i = first; i <= last; i++) {
a.pb(b[i]);
}
}
bool connected(vector<int> v1, vector<int> v2)
{
v1.resize(unique(v1.begin(), v1.end()) - v1.begin());
v2.resize(unique(v2.begin(), v2.end()) - v2.begin());
return are_connected(v1, v2);
}
vector<int> longest_trip(int N, int D)
{
vector<int> v1, v2;
v1.pb(0);
v2.pb(1);
for (int i = 2; i < N; i++) {
if (connected({v1.back()}, {i})) {
v1.pb(i);
}
else if (connected({v2.back()}, {i})) {
v2.pb(i);
}
else {
for (int j = v2.size() - 1; j >= 0; j--) {
v1.pb(v2[j]);
}
v2.clear();
v2.pb(i);
}
if (v1.size() < v2.size()) {
swap(v1, v2);
}
}
vector<int> res;
if (connected(v1, v2)) {
if (connected({v1.front(), v1.back()}, {v2.front(), v2.back()})) {
// Some endpoints are connected
if (connected({v1.front()}, {v2.front(), v2.back()})) {
reverse(v1.begin(), v1.end());
}
if (connected({v1.back()}, {v2.back()})) {
reverse(v2.begin(), v2.end());
}
extend(res, v1, 0, v1.size() - 1);
extend(res, v2, 0, v2.size() - 1);
}
else {
// No endpoints are connected => v1 and v2 are 2 cycles
int l = 0;
int r = v1.size();
while (l + 1 < r) {
int mid = (l + r) / 2;
if (connected(vector<int>(v1.begin(), v1.begin() + mid), v2)) {
r = mid;
}
else {
l = mid;
}
}
int p1 = l;
l = 0;
r = v2.size();
while (l + 1 < r) {
int mid = (l + r) / 2;
if (connected(vector<int>(v2.begin(), v2.begin() + mid), {v1[p1]})) {
r = mid;
}
else {
l = mid;
}
}
int p2 = l;
extend(res, v1, p1 + 1, v1.size() - 1);
extend(res, v1, 0, p1);
extend(res, v2, p2, v2.size() - 1);
extend(res, v2, 0, p2 - 1);
}
}
else {
res = v1;
}
return res;
}
