#include "longesttrip.h"
#include <bits/stdc++.h>
using namespace std;
mt19937 rng(random_device{}());
int get(vector<int> a, const vector<int>& b) {
if(a.size() == 1) return a.back();
vector<int> a2;
while(a.size() > a2.size())
a2.push_back(a.back()), a.pop_back();
reverse(a2.begin(), a2.end());
if(are_connected(a, b))
return get(a, b);
return get(a2, b);
}
void ajusta(vector<int>& a, int a1) {
vector<int> aux;
while(a.back() != a1) {
aux.push_back(a.back());
a.pop_back();
}
reverse(aux.begin(), aux.end());
for(int x : a)
aux.push_back(x);
a = aux;
}
vector<int> longest_trip(int N, int D)
{
vector<int> perm(N); iota(perm.begin(), perm.end(), 0);
shuffle(perm.begin(), perm.end(), rng);
vector<int> a = { perm.back() }; perm.pop_back();
vector<int> b;
bool topos_disconexos = 1;
while(perm.size()) {
int x = perm.back();
perm.pop_back();
if(are_connected({x}, {a.back()})) {
a.push_back(x);
topos_disconexos = b.size() == 0;
} else if(topos_disconexos) {
b.push_back(x);
} else {
if(are_connected({x}, {b.back()})) {
b.push_back(x);
topos_disconexos = 1;
} else {
reverse(b.begin(), b.end());
for(int k : b)
a.push_back(k);
if(b.size() == 1)
topos_disconexos = 1;
b.clear();
b.push_back(x);
}
}
}
if(!b.size()) return a;
for(int i = 0; i < 2; i++, reverse(a.begin(), a.end())) {
for(int j = 0; j < 2; j++, reverse(b.begin(), b.end())) {
if(are_connected({a.back()}, {b.front()})) {
for(int x : b)
a.push_back(x);
return a;
}
}
}
if(!are_connected(a, b))
return a.size() > b.size() ? a : b;
int a1 = get(a, b);
int b1 = get(b, {a1});
ajusta(a, a1);
ajusta(b, b1);
reverse(b.begin(), b.end());
for(int x : b)
a.push_back(x);
b.clear();
return a;
}
