Problem p02964 (C++)

Buggy submission (status: Runtime Error):
#include <bits/stdc++.h>
using namespace std;
using lint = long long;
const lint mod = 1e9 + 7;
#define all(x) (x).begin(), (x).end()
#define bitcount(n) __builtin_popcountl((lint)(n))
#define fcout cout << fixed << setprecision(15)
#define highest(x) (63 - __builtin_clzl(x))
template <class T> inline void YES(T condition) {
  if (condition)
    cout << "YES" << endl;
  else
    cout << "NO" << endl;
}
template <class T> inline void Yes(T condition) {
  if (condition)
    cout << "Yes" << endl;
  else
    cout << "No" << endl;
}
template <class T = string, class U = char>
int character_count(T text, U character) {
  int ans = 0;
  for (U i : text) {
    ans += (i == character);
  }
  return ans;
}
lint power(lint base, lint exponent, lint module) {
  if (exponent % 2) {
    return power(base, exponent - 1, module) * base % module;
  } else if (exponent) {
    lint root_ans = power(base, exponent / 2, module);
    return root_ans * root_ans % module;
  } else {
    return 1;
  }
}
struct position {
  int y, x;
};
position mv[4] = {
    {0, -1},
    {1, 0},
    {0, 1},
    {-1, 0}}; // double euclidean(position first, position second){ return
              // sqrt((second.x - first.x) * (second.x - first.x) + (second.y -
              // first.y) * (second.y - first.y)); }
template <class T, class U> string to_string(pair<T, U> x) {
  return to_string(x.first) + "," + to_string(x.second);
}
string to_string(string x) { return x; }
template <class itr> void array_output(itr start, itr goal) {
  string ans;
  for (auto i = start; i != goal; i++)
    ans += to_string(*i) + " ";
  if (!ans.empty())
    ans.pop_back();
  cout << ans << endl;
}
template <class itr> void cins(itr first, itr last) {
  for (auto i = first; i != last; i++) {
    cin >> (*i);
  }
}
template <class T> T gcd(T a, T b) {
  if (a && b) {
    return gcd(min(a, b), max(a, b) % min(a, b));
  } else {
    return a;
  }
}
template <class T> T lcm(T a, T b) { return a / gcd(a, b) * b; }
struct combination {
  vector<lint> fact, inv;
  combination(int sz) : fact(sz + 1), inv(sz + 1) {
    fact[0] = 1;
    for (int i = 1; i <= sz; i++) {
      fact[i] = fact[i - 1] * i % mod;
    }
    inv[sz] = power(fact[sz], mod - 2, mod);
    for (int i = sz - 1; i >= 0; i--) {
      inv[i] = inv[i + 1] * (i + 1) % mod;
    }
  }
  lint C(int p, int q) const {
    if (q < 0 || p < q)
      return 0;
    return (fact[p] * inv[q] % mod * inv[p - q] % mod);
  }
};
template <class itr> bool next_sequence(itr first, itr last, int max_bound) {
  itr now = last;
  while (now != first) {
    now--;
    (*now)++;
    if ((*now) == max_bound) {
      (*now) = 0;
    } else {
      return true;
    }
  }
  return false;
}

int main() {
  int N;
  lint K;
  cin >> N >> K;
  int A[N];
  cins(A, A + N);
  vector<int> nums(2e5 + 100, -1);
  int ptr[N];
  for (int i = 0; i < N * 2; i++) {
    int a = A[i % N];
    if (nums[a] != -1 && nums[a] < N) {
      ptr[nums[a]] = i + 1;
    }
    nums[a] = i;
  }
  int loop = 0, now = 0;
  while (true) {
    loop += ptr[now] / N;
    now = ptr[now] % N;
    if (now == 0) {
      break;
    }
  }
  K %= loop;
  if (K == 0) {
    cout << endl;
    return 0;
  }
  now = 0;
  int loop_cnt = 0;
  while (true) {
    loop_cnt += ptr[now] / N;
    if (loop_cnt >= K) {
      break;
    }
    now = ptr[now] % N;
  }
  vector<int> nums_cnt(2e5 + 100, 0), que;
  for (int i = now; i < N; i++) {
    if (nums_cnt[A[i]]) {
      while (que.back() != A[i]) {
        que.pop_back();
      }
      que.pop_back();
    } else {
      que.push_back(A[i]);
    }
    nums_cnt[A[i]] ^= 1;
  }
  array_output(all(que));
}


Fixed submission:
#include <bits/stdc++.h>
using namespace std;
using lint = long long;
const lint mod = 1e9 + 7;
#define all(x) (x).begin(), (x).end()
#define bitcount(n) __builtin_popcountl((lint)(n))
#define fcout cout << fixed << setprecision(15)
#define highest(x) (63 - __builtin_clzl(x))
template <class T> inline void YES(T condition) {
  if (condition)
    cout << "YES" << endl;
  else
    cout << "NO" << endl;
}
template <class T> inline void Yes(T condition) {
  if (condition)
    cout << "Yes" << endl;
  else
    cout << "No" << endl;
}
template <class T = string, class U = char>
int character_count(T text, U character) {
  int ans = 0;
  for (U i : text) {
    ans += (i == character);
  }
  return ans;
}
lint power(lint base, lint exponent, lint module) {
  if (exponent % 2) {
    return power(base, exponent - 1, module) * base % module;
  } else if (exponent) {
    lint root_ans = power(base, exponent / 2, module);
    return root_ans * root_ans % module;
  } else {
    return 1;
  }
}
struct position {
  int y, x;
};
position mv[4] = {
    {0, -1},
    {1, 0},
    {0, 1},
    {-1, 0}}; // double euclidean(position first, position second){ return
              // sqrt((second.x - first.x) * (second.x - first.x) + (second.y -
              // first.y) * (second.y - first.y)); }
template <class T, class U> string to_string(pair<T, U> x) {
  return to_string(x.first) + "," + to_string(x.second);
}
string to_string(string x) { return x; }
template <class itr> void array_output(itr start, itr goal) {
  string ans;
  for (auto i = start; i != goal; i++)
    ans += to_string(*i) + " ";
  if (!ans.empty())
    ans.pop_back();
  cout << ans << endl;
}
template <class itr> void cins(itr first, itr last) {
  for (auto i = first; i != last; i++) {
    cin >> (*i);
  }
}
template <class T> T gcd(T a, T b) {
  if (a && b) {
    return gcd(min(a, b), max(a, b) % min(a, b));
  } else {
    return a;
  }
}
template <class T> T lcm(T a, T b) { return a / gcd(a, b) * b; }
struct combination {
  vector<lint> fact, inv;
  combination(int sz) : fact(sz + 1), inv(sz + 1) {
    fact[0] = 1;
    for (int i = 1; i <= sz; i++) {
      fact[i] = fact[i - 1] * i % mod;
    }
    inv[sz] = power(fact[sz], mod - 2, mod);
    for (int i = sz - 1; i >= 0; i--) {
      inv[i] = inv[i + 1] * (i + 1) % mod;
    }
  }
  lint C(int p, int q) const {
    if (q < 0 || p < q)
      return 0;
    return (fact[p] * inv[q] % mod * inv[p - q] % mod);
  }
};
template <class itr> bool next_sequence(itr first, itr last, int max_bound) {
  itr now = last;
  while (now != first) {
    now--;
    (*now)++;
    if ((*now) == max_bound) {
      (*now) = 0;
    } else {
      return true;
    }
  }
  return false;
}

int main() {
  int N;
  lint K;
  cin >> N >> K;
  int A[N];
  cins(A, A + N);
  vector<int> nums(2e5 + 100, -1);
  int ptr[N];
  for (int i = 0; i < N * 2; i++) {
    int a = A[i % N];
    if (nums[a] != -1 && nums[a] < N) {
      ptr[nums[a]] = i + 1;
    }
    nums[a] = i;
  }
  int loop = 0, now = 0;
  while (true) {
    loop += ptr[now] / N;
    now = ptr[now] % N;
    if (now == 0) {
      break;
    }
  }
  K %= loop;
  if (K == 0) {
    cout << endl;
    return 0;
  }
  now = 0;
  int loop_cnt = 0;
  while (true) {
    loop_cnt += ptr[now] / N;
    if (loop_cnt >= K) {
      break;
    }
    now = ptr[now] % N;
  }
  vector<int> nums_cnt(2e5 + 100, 0), que;
  for (int i = now; i < N; i++) {
    if (nums_cnt[A[i]]) {
      while (que.back() != A[i]) {
        nums_cnt[que.back()] ^= 1;
        que.pop_back();
      }
      que.pop_back();
    } else {
      que.push_back(A[i]);
    }
    nums_cnt[A[i]] ^= 1;
  }
  array_output(all(que));
}