Problem p02809 (C++)

Buggy submission (status: Runtime Error):
#include <algorithm>
#include <bitset>
#include <cassert>
#include <ciso646>
#include <cmath>
#include <complex>
#include <cstdio>
#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;
const ll mod = 1000000007;
const ll INF = (1e+18) + 7;
typedef pair<int, int> P;
#define stop                                                                   \
  char nyaa;                                                                   \
  cin >> nyaa;
#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++)
#define all(v) (v).begin(), (v).end()
typedef pair<ll, ll> LP;
typedef long double ld;
typedef pair<ld, ld> LDP;
const ld eps = 1e-6;
const ld pi = acos(-1.0);
// typedef vector<vector<ll>> mat;
typedef vector<int> vec;

ll mod_pow(ll a, ll n) {
  ll res = 1;
  while (n) {
    if (n & 1)
      res = res * a % mod;
    a = a * a % mod;
    n >>= 1;
  }
  return res;
}

struct modint {
  ll n;
  modint() : n(0) { ; }
  modint(ll m) : n(m) {
    if (n >= mod)
      n %= mod;
    else if (n < 0)
      n = (n % mod + mod) % mod;
  }
  operator int() { return n; }
};
bool operator==(modint a, modint b) { return a.n == b.n; }
modint operator+=(modint &a, modint b) {
  a.n += b.n;
  if (a.n >= mod)
    a.n -= mod;
  return a;
}
modint operator-=(modint &a, modint b) {
  a.n -= b.n;
  if (a.n < 0)
    a.n += mod;
  return a;
}
modint operator*=(modint &a, modint b) {
  a.n = ((ll)a.n * b.n) % mod;
  return a;
}
modint operator+(modint a, modint b) { return a += b; }
modint operator-(modint a, modint b) { return a -= b; }
modint operator*(modint a, modint b) { return a *= b; }
modint operator^(modint a, int n) {
  if (n == 0)
    return modint(1);
  modint res = (a * a) ^ (n / 2);
  if (n % 2)
    res = res * a;
  return res;
}

ll inv(ll a, ll p) { return (a == 1 ? 1 : (1 - p * inv(p % a, a)) / a + p); }
modint operator/(modint a, modint b) { return a * modint(inv(b, mod)); }

const int max_n = 1 << 20;
modint fact[max_n], factinv[max_n];
void init() {
  fact[0] = modint(1);
  for (int i = 0; i < max_n - 1; i++) {
    fact[i + 1] = fact[i] * modint(i + 1);
  }
  factinv[max_n - 1] = modint(1) / fact[max_n - 1];
  for (int i = max_n - 2; i >= 0; i--) {
    factinv[i] = factinv[i + 1] * modint(i + 1);
  }
}
modint comb(int a, int b) {
  if (a < 0 || b < 0 || a < b)
    return 0;
  return fact[a] * factinv[b] * factinv[a - b];
}

int a[1 << 17];
vector<int> calc(vector<int> v, int pre) {
  sort(v.begin(), v.end());
  while (true) {
    bool valid = true;
    if (v[0] == pre)
      valid = false;
    rep(i, v.size() - 1) {
      if (v[i + 1] == a[v[i]])
        valid = false;
    }
    if (valid)
      return v;
    if (!next_permutation(v.begin(), v.end()))
      break;
  }
  return {};
}
modint dp[1001];
modint cop[1001];
void solve() {
  int n;
  cin >> n;
  rep(i, n) {
    cin >> a[i];
    a[i]--;
  }
  if (n == 2) {
    cout << -1 << endl;
    return;
  }
  if (n <= 6) {
    vector<int> ori(n);
    rep(i, n) ori[i] = i;
    vector<int> ans = calc(ori, -1);
    rep(i, n) {
      if (i > 0)
        cout << " ";
      cout << ans[i] + 1;
    }
    cout << endl;
    return;
  }
  vector<int> ans;
  set<int> st;
  rep(i, n) st.insert(i);
  int out = -1;
  rep(i, n - 6) {
    int z = *st.begin();
    if (out == z) {
      z = *(++st.begin());
    }
    ans.push_back(z);
    st.erase(z);
    out = a[z];
  }
  vector<int> v;
  for (auto &&z : st) {
    v.push_back(z);
  }
  vector<int> las = calc(v, out);
  rep(i, las.size()) ans.push_back(las[i]);
  assert(ans.size() == n);
  rep(i, n) {
    if (i > 0)
      cout << " ";
    cout << ans[i] + 1;
  }
  cout << endl;
}

signed main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  // cout << fixed << setprecision(17);
  init();
  // int t; cin >> t; rep(i, t)solve();
  solve();
  stop return 0;
}


Fixed submission:
#include <algorithm>
#include <bitset>
#include <cassert>
#include <ciso646>
#include <cmath>
#include <complex>
#include <cstdio>
#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;
const ll mod = 1000000007;
const ll INF = (1e+18) + 7;
typedef pair<int, int> P;
#define stop                                                                   \
  char nyaa;                                                                   \
  cin >> nyaa;
#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++)
#define all(v) (v).begin(), (v).end()
typedef pair<ll, ll> LP;
typedef long double ld;
typedef pair<ld, ld> LDP;
const ld eps = 1e-6;
const ld pi = acos(-1.0);
// typedef vector<vector<ll>> mat;
typedef vector<int> vec;

ll mod_pow(ll a, ll n) {
  ll res = 1;
  while (n) {
    if (n & 1)
      res = res * a % mod;
    a = a * a % mod;
    n >>= 1;
  }
  return res;
}

struct modint {
  ll n;
  modint() : n(0) { ; }
  modint(ll m) : n(m) {
    if (n >= mod)
      n %= mod;
    else if (n < 0)
      n = (n % mod + mod) % mod;
  }
  operator int() { return n; }
};
bool operator==(modint a, modint b) { return a.n == b.n; }
modint operator+=(modint &a, modint b) {
  a.n += b.n;
  if (a.n >= mod)
    a.n -= mod;
  return a;
}
modint operator-=(modint &a, modint b) {
  a.n -= b.n;
  if (a.n < 0)
    a.n += mod;
  return a;
}
modint operator*=(modint &a, modint b) {
  a.n = ((ll)a.n * b.n) % mod;
  return a;
}
modint operator+(modint a, modint b) { return a += b; }
modint operator-(modint a, modint b) { return a -= b; }
modint operator*(modint a, modint b) { return a *= b; }
modint operator^(modint a, int n) {
  if (n == 0)
    return modint(1);
  modint res = (a * a) ^ (n / 2);
  if (n % 2)
    res = res * a;
  return res;
}

ll inv(ll a, ll p) { return (a == 1 ? 1 : (1 - p * inv(p % a, a)) / a + p); }
modint operator/(modint a, modint b) { return a * modint(inv(b, mod)); }

const int max_n = 1 << 20;
modint fact[max_n], factinv[max_n];
void init() {
  fact[0] = modint(1);
  for (int i = 0; i < max_n - 1; i++) {
    fact[i + 1] = fact[i] * modint(i + 1);
  }
  factinv[max_n - 1] = modint(1) / fact[max_n - 1];
  for (int i = max_n - 2; i >= 0; i--) {
    factinv[i] = factinv[i + 1] * modint(i + 1);
  }
}
modint comb(int a, int b) {
  if (a < 0 || b < 0 || a < b)
    return 0;
  return fact[a] * factinv[b] * factinv[a - b];
}

int a[1 << 17];
vector<int> calc(vector<int> v, int pre) {
  sort(v.begin(), v.end());
  while (true) {
    bool valid = true;
    if (v[0] == pre)
      valid = false;
    rep(i, v.size() - 1) {
      if (v[i + 1] == a[v[i]])
        valid = false;
    }
    if (valid)
      return v;
    if (!next_permutation(v.begin(), v.end()))
      break;
  }
  return {};
}
modint dp[1001];
modint cop[1001];
void solve() {
  int n;
  cin >> n;
  rep(i, n) {
    cin >> a[i];
    a[i]--;
  }
  if (n == 2) {
    cout << -1 << endl;
    return;
  }
  if (n <= 6) {
    vector<int> ori(n);
    rep(i, n) ori[i] = i;
    vector<int> ans = calc(ori, -1);
    rep(i, n) {
      if (i > 0)
        cout << " ";
      cout << ans[i] + 1;
    }
    cout << endl;
    return;
  }
  vector<int> ans;
  set<int> st;
  rep(i, n) st.insert(i);
  int out = -1;
  rep(i, n - 6) {
    int z = *st.begin();
    if (out == z) {
      z = *(++st.begin());
    }
    ans.push_back(z);
    st.erase(z);
    out = a[z];
  }
  vector<int> v;
  for (auto &&z : st) {
    v.push_back(z);
  }
  vector<int> las = calc(v, out);

  if (las.empty()) {
    int chk;
    if (a[v[0]] == a[v[1]])
      chk = a[v[0]];
    else
      chk = a[v[2]];
    rep(i, n - 6) {
      if (a[ans.back()] == chk) {
        v.push_back(ans.back());
        ans.pop_back();
      } else
        break;
    }
    ans.push_back(chk);
    sort(v.begin(), v.end());
    if (a[chk] == v[0])
      swap(v[0], v[1]);
    rep(i, v.size()) if (v[i] != chk) ans.push_back(v[i]);
  } else {
    rep(i, las.size()) ans.push_back(las[i]);
  }
  // assert(ans.size() == n);
  rep(i, n) {
    if (i > 0)
      cout << " ";
    cout << ans[i] + 1;
  }
  cout << endl;
}

signed main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  // cout << fixed << setprecision(17);
  init();
  // int t; cin >> t; rep(i, t)solve();
  solve();
  stop return 0;
}