Problem p02809 (C++)

Buggy submission (status: Runtime Error):
/**
 *    author:  otera
 **/
#include <algorithm>
#include <bitset>
#include <cassert>
#include <ciso646>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstring>
#include <deque>
#include <functional>
#include <iomanip>
#include <iostream>
#include <map>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <unordered_map>
#include <utility>
#include <vector>
using namespace std;

// #define int long long
typedef long long ll;
typedef unsigned long long ul;
typedef unsigned int ui;
typedef long double ld;
const int inf = 1e9 + 7;
const ll INF = 1LL << 60;
const ll mod = 1e9 + 7;
#define rep(i, n) for (int i = 0; i < n; i++)
#define per(i, n) for (int i = n - 1; i >= 0; i--)
#define Rep(i, sta, n) for (int i = sta; i < n; i++)
#define rep1(i, n) for (int i = 1; i <= n; i++)
#define per1(i, n) for (int i = n; i >= 1; i--)
#define Rep1(i, sta, n) for (int i = sta; i <= n; i++)
typedef complex<ld> Point;
const ld eps = 1e-8;
const ld pi = acos(-1.0);
typedef pair<int, int> P;
typedef pair<ld, ld> LDP;
typedef pair<ll, ll> LP;
#define fr first
#define sc second
#define all(c) c.begin(), c.end()
#define pb push_back
#define debug(x) cerr << #x << " = " << (x) << endl;
template <class T> inline bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T> inline bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return 1;
  }
  return 0;
}

void fail() {
  cout << -1 << endl;
  exit(0);
}

void out(vector<int> x) {
  rep(i, (int)x.size()) {
    if (i)
      cout << " ";
    cout << x[i] + 1;
  }
  cout << endl;
  exit(0);
}

void solve() {
  int n;
  cin >> n;
  vector<int> a(n);
  rep(i, n) {
    cin >> a[i];
    --a[i];
  }
  set<int> se;
  for (int i = 1; i < n; ++i)
    se.insert(i);
  vector<int> ans(1, 0);
  for (int i = 1; i < n - 1; ++i) {
    auto ite = se.begin();
    if (*ite == a[ans.back()])
      ++ite;
    ans.push_back(*ite);
    se.erase(ite);
  }
  int b = *se.begin();
  if (b != a[ans.back()]) {
    ans.push_back(b);
    out(ans);
  }
  set<int> pool;
  while (ans.size() and a[ans.back()] == b) {
    pool.insert(ans.back());
    ans.pop_back();
  }
  if (pool.size() == 1) {
    vector<int> p;
    p.push_back(b);
    p.push_back(*pool.begin());
    p.push_back(ans.back());
    ans.pop_back();
    sort(all(p));
    auto tmp = ans;
    vector<int> res = {n + 1};
    do {
      for (int x : p)
        tmp.push_back(x);
      bool ok = 1;
      rep(i, n - 1) {
        if (tmp[i + 1] == a[tmp[i]])
          ok = 0;
      }
      if (ok)
        chmin(res, tmp);
      rep(i, 3) tmp.pop_back();
    } while (next_permutation(all(p)));
    ans = res;
  } else {
    ans.push_back(b);
    while (pool.size()) {
      auto ite = pool.begin();
      if (*ite == a[ans.back()])
        ++ite;
      ans.push_back(*ite);
      pool.erase(ite);
    }
  }
  out(ans);
}

signed main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  // cout << fixed << setprecision(10);
  // int t; cin >> t; rep(i, t)solve();
  solve();
  return 0;
}

Fixed submission:
/**
 *    author:  otera
 **/
#include <algorithm>
#include <bitset>
#include <cassert>
#include <ciso646>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstring>
#include <deque>
#include <functional>
#include <iomanip>
#include <iostream>
#include <map>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <unordered_map>
#include <utility>
#include <vector>
using namespace std;

// #define int long long
typedef long long ll;
typedef unsigned long long ul;
typedef unsigned int ui;
typedef long double ld;
const int inf = 1e9 + 7;
const ll INF = 1LL << 60;
const ll mod = 1e9 + 7;
#define rep(i, n) for (int i = 0; i < n; i++)
#define per(i, n) for (int i = n - 1; i >= 0; i--)
#define Rep(i, sta, n) for (int i = sta; i < n; i++)
#define rep1(i, n) for (int i = 1; i <= n; i++)
#define per1(i, n) for (int i = n; i >= 1; i--)
#define Rep1(i, sta, n) for (int i = sta; i <= n; i++)
typedef complex<ld> Point;
const ld eps = 1e-8;
const ld pi = acos(-1.0);
typedef pair<int, int> P;
typedef pair<ld, ld> LDP;
typedef pair<ll, ll> LP;
#define fr first
#define sc second
#define all(c) c.begin(), c.end()
#define pb push_back
#define debug(x) cerr << #x << " = " << (x) << endl;
template <class T> inline bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T> inline bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return 1;
  }
  return 0;
}

void fail() {
  cout << -1 << endl;
  exit(0);
}

void out(vector<int> x) {
  rep(i, (int)x.size()) {
    if (i)
      cout << " ";
    cout << x[i] + 1;
  }
  cout << endl;
  exit(0);
}

void solve() {
  int n;
  cin >> n;
  vector<int> a(n);
  rep(i, n) {
    cin >> a[i];
    --a[i];
  }
  set<int> se;
  for (int i = 1; i < n; ++i)
    se.insert(i);
  vector<int> ans(1, 0);
  for (int i = 1; i < n - 1; ++i) {
    auto ite = se.begin();
    if (*ite == a[ans.back()])
      ++ite;
    ans.push_back(*ite);
    se.erase(ite);
  }
  int b = *se.begin();
  if (b != a[ans.back()]) {
    ans.push_back(b);
    out(ans);
  }
  set<int> pool;
  while (ans.size() and a[ans.back()] == b) {
    pool.insert(ans.back());
    ans.pop_back();
  }
  if (pool.size() == 1) {
    if (n == 2)
      fail();
    vector<int> p;
    p.push_back(b);
    p.push_back(*pool.begin());
    p.push_back(ans.back());
    ans.pop_back();
    sort(all(p));
    auto tmp = ans;
    vector<int> res = {n + 1};
    do {
      for (int x : p)
        tmp.push_back(x);
      bool ok = 1;
      rep(i, n - 1) {
        if (tmp[i + 1] == a[tmp[i]])
          ok = 0;
      }
      if (ok)
        chmin(res, tmp);
      rep(i, 3) tmp.pop_back();
    } while (next_permutation(all(p)));
    ans = res;
  } else {
    ans.push_back(b);
    while (pool.size()) {
      auto ite = pool.begin();
      if (*ite == a[ans.back()])
        ++ite;
      ans.push_back(*ite);
      pool.erase(ite);
    }
  }
  out(ans);
}

signed main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  // cout << fixed << setprecision(10);
  // int t; cin >> t; rep(i, t)solve();
  solve();
  return 0;
}