Problem p02964 (C++)

Buggy submission (status: Runtime Error):
#include <algorithm>
#include <bitset>
#include <cstring>
#include <iomanip>
#include <iostream>
#include <limits>
#include <list>
#include <map>
#include <math.h>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <tuple>
#include <vector>
using namespace std;
#define fast_io                                                                \
  ios_base::sync_with_stdio(false);                                            \
  cin.tie(0);                                                                  \
  cout.tie(0);
#define MOD (long long int)(1e9 + 7)
#define ll long long int
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define reps(i, n) for (int i = 1; i <= (int)(n); i++)
#define REP(i, n) for (int i = n - 1; i >= 0; i--)
#define REPS(i, n) for (int i = n; i > 0; i--)
#define INF (int)(1123456789)
#define LINF (long long int)(112345678901234567)
#define chmax(a, b) a = (((a) < (b)) ? (b) : (a))
#define chmin(a, b) a = (((a) > (b)) ? (b) : (a))
#define all(v) v.begin(), v.end()

typedef pair<int, int> Pii;
typedef pair<ll, ll> Pll;

ll mpow(ll a, ll b) {
  if (b == 0)
    return 1;
  else if (b % 2 == 0) {
    ll memo = mpow(a, b / 2);
    return memo * memo % MOD;
  } else
    return mpow(a, b - 1) * a % MOD;
}
ll lpow(ll a, ll b) {
  if (b == 0)
    return 1;
  else if (b % 2 == 0) {
    ll memo = lpow(a, b / 2);
    return memo * memo;
  } else
    return lpow(a, b - 1) * a;
}
ll gcd(ll a, ll b) {
  if (b == 0)
    return a;
  else
    return gcd(b, a % b);
}
vector<ll> kaijo_memo;
ll kaijo(ll n) {
  if (kaijo_memo.size() > n)
    return kaijo_memo[n];
  if (kaijo_memo.size() == 0)
    kaijo_memo.push_back(1);
  while (kaijo_memo.size() <= n)
    kaijo_memo.push_back(kaijo_memo[kaijo_memo.size() - 1] * kaijo_memo.size() %
                         MOD);
  return kaijo_memo[n];
}
vector<ll> gyaku_kaijo_memo;
ll gyaku_kaijo(ll n) {
  if (gyaku_kaijo_memo.size() > n)
    return gyaku_kaijo_memo[n];
  if (gyaku_kaijo_memo.size() == 0)
    gyaku_kaijo_memo.push_back(1);
  while (gyaku_kaijo_memo.size() <= n)
    gyaku_kaijo_memo.push_back(gyaku_kaijo_memo[gyaku_kaijo_memo.size() - 1] *
                               mpow(gyaku_kaijo_memo.size(), MOD - 2) % MOD);
  return gyaku_kaijo_memo[n];
}

ll nCr(ll n, ll r) {
  if (n == r)
    return 1; // 0個の丸と-1個の棒みたいな時に時に効く？不安.
  if (n < r || r < 0)
    return 0;
  ll ret = 1;
  ret *= kaijo(n);
  ret %= MOD;
  ret *= gyaku_kaijo(r);
  ret %= MOD;
  ret *= gyaku_kaijo(n - r);
  ret %= MOD;
  return ret;
}

bool used[(int)2e5 + 3];
void simulate(ll k, int now, vector<ll> &A) {

  rep(i, 2e5 + 3) { used[i] = false; }
  vector<ll> ans;
  while (now < A.size()) {
    ll a = A[now];
    if (used[a]) {
      while (used[a]) {
        used[ans.back()] = false;
        ans.pop_back();
      }
    } else {
      ans.push_back(a);
      used[a] = true;
    }
    now++;
  }
  rep(i, ans.size()) { cout << ans[i] + 1 << " "; }
  cout << endl;
}

int main(void) {
  fast_io cout << fixed << setprecision(15);

  ll n, k;
  cin >> n >> k;
  vector<ll> A(n), Next(n), memo(n);
  rep(i, n) {
    cin >> A[i];
    A[i]--;
  }
  REP(i, n) { memo[A[i]] = i; }
  REP(i, n) {
    Next[i] = memo[A[i]];
    memo[A[i]] = i;
  }
  vector<bool> checked(n, false);
  ll now = 0;
  while (k >= 2) {
    ll next = Next[now];
    if (next <= now)
      k--;
    if (next == n - 1)
      k--;
    now = (next + 1) % n;
    if (checked[next])
      break;
    checked[next] = true;
  }
  if (k == 0) {
    return 0;
  }
  if (k == 1) {
    simulate(k, now, A);
    return 0;
  }

  ll goal = now;

  ll count = 0;
  while (k >= 2) {
    ll next = Next[now];
    if (next <= now)
      count++;
    if (next == n - 1)
      count++;
    now = (next + 1) % n;
    if (now == goal)
      break;
  }
  if (k == 0) {
    return 0;
  }
  if (k == 1) {
    simulate(k, now, A);
    return 0;
  }

  k = k % count;
  while (k >= 2) {
    ll next = Next[now];
    if (next <= now)
      k--;
    if (next == n - 1)
      k--;
    now = (next + 1) % n;
  }
  if (k == 0) {
    return 0;
  }
  if (k == 1) {
    simulate(k, now, A);
    return 0;
  }

  return 0;
}


Fixed submission:
#include <algorithm>
#include <bitset>
#include <cstring>
#include <iomanip>
#include <iostream>
#include <limits>
#include <list>
#include <map>
#include <math.h>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <tuple>
#include <vector>
using namespace std;
#define fast_io                                                                \
  ios_base::sync_with_stdio(false);                                            \
  cin.tie(0);                                                                  \
  cout.tie(0);
#define MOD (long long int)(1e9 + 7)
#define ll long long int
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define reps(i, n) for (int i = 1; i <= (int)(n); i++)
#define REP(i, n) for (int i = n - 1; i >= 0; i--)
#define REPS(i, n) for (int i = n; i > 0; i--)
#define INF (int)(1123456789)
#define LINF (long long int)(112345678901234567)
#define chmax(a, b) a = (((a) < (b)) ? (b) : (a))
#define chmin(a, b) a = (((a) > (b)) ? (b) : (a))
#define all(v) v.begin(), v.end()

typedef pair<int, int> Pii;
typedef pair<ll, ll> Pll;

ll mpow(ll a, ll b) {
  if (b == 0)
    return 1;
  else if (b % 2 == 0) {
    ll memo = mpow(a, b / 2);
    return memo * memo % MOD;
  } else
    return mpow(a, b - 1) * a % MOD;
}
ll lpow(ll a, ll b) {
  if (b == 0)
    return 1;
  else if (b % 2 == 0) {
    ll memo = lpow(a, b / 2);
    return memo * memo;
  } else
    return lpow(a, b - 1) * a;
}
ll gcd(ll a, ll b) {
  if (b == 0)
    return a;
  else
    return gcd(b, a % b);
}
vector<ll> kaijo_memo;
ll kaijo(ll n) {
  if (kaijo_memo.size() > n)
    return kaijo_memo[n];
  if (kaijo_memo.size() == 0)
    kaijo_memo.push_back(1);
  while (kaijo_memo.size() <= n)
    kaijo_memo.push_back(kaijo_memo[kaijo_memo.size() - 1] * kaijo_memo.size() %
                         MOD);
  return kaijo_memo[n];
}
vector<ll> gyaku_kaijo_memo;
ll gyaku_kaijo(ll n) {
  if (gyaku_kaijo_memo.size() > n)
    return gyaku_kaijo_memo[n];
  if (gyaku_kaijo_memo.size() == 0)
    gyaku_kaijo_memo.push_back(1);
  while (gyaku_kaijo_memo.size() <= n)
    gyaku_kaijo_memo.push_back(gyaku_kaijo_memo[gyaku_kaijo_memo.size() - 1] *
                               mpow(gyaku_kaijo_memo.size(), MOD - 2) % MOD);
  return gyaku_kaijo_memo[n];
}

ll nCr(ll n, ll r) {
  if (n == r)
    return 1; // 0個の丸と-1個の棒みたいな時に時に効く？不安.
  if (n < r || r < 0)
    return 0;
  ll ret = 1;
  ret *= kaijo(n);
  ret %= MOD;
  ret *= gyaku_kaijo(r);
  ret %= MOD;
  ret *= gyaku_kaijo(n - r);
  ret %= MOD;
  return ret;
}

bool used[(int)2e5 + 3];
void simulate(ll k, int now, vector<ll> &A) {

  rep(i, 2e5 + 3) { used[i] = false; }
  vector<ll> ans;
  while (now < A.size()) {
    ll a = A[now];
    if (used[a]) {
      while (used[a]) {
        used[ans.back()] = false;
        ans.pop_back();
      }
    } else {
      ans.push_back(a);
      used[a] = true;
    }
    now++;
  }
  rep(i, ans.size()) { cout << ans[i] + 1 << " "; }
  cout << endl;
}

int main(void) {
  fast_io cout << fixed << setprecision(15);

  ll n, k;
  cin >> n >> k;
  vector<ll> A(n), Next(n), memo((int)2e5 + 4);
  rep(i, n) {
    cin >> A[i];
    A[i]--;
  }
  REP(i, n) { memo[A[i]] = i; }
  REP(i, n) {
    Next[i] = memo[A[i]];
    memo[A[i]] = i;
  }
  vector<bool> checked(n, false);
  ll now = 0;
  while (k >= 2) {
    ll next = Next[now];
    if (next <= now)
      k--;
    if (next == n - 1)
      k--;
    now = (next + 1) % n;
    if (checked[next])
      break;
    checked[next] = true;
  }
  if (k == 0) {
    return 0;
  }
  if (k == 1) {
    simulate(k, now, A);
    return 0;
  }

  ll goal = now;

  ll count = 0;
  while (k >= 2) {
    ll next = Next[now];
    if (next <= now)
      count++;
    if (next == n - 1)
      count++;
    now = (next + 1) % n;
    if (now == goal)
      break;
  }
  if (k == 0) {
    return 0;
  }
  if (k == 1) {
    simulate(k, now, A);
    return 0;
  }

  k = k % count;
  while (k >= 2) {
    ll next = Next[now];
    if (next <= now)
      k--;
    if (next == n - 1)
      k--;
    now = (next + 1) % n;
  }
  if (k == 0) {
    return 0;
  }
  if (k == 1) {
    simulate(k, now, A);
    return 0;
  }

  return 0;
}