Problem p02684 (C++) — buggy submission, verdict: Runtime Error

/*~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=
*$* WRITER:kakitamasziru/OxOmisosiru *$*
~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=*/
#ifdef LOCAL_JUDGE
#define _GLIBCXX_DEBUG // FOR THE DEBUG! COMMENT OUT THIS WHEN SUBMITTING!
#endif
/* I REALLY HOPE MY WISH REACH YOU , ATCODER'S ONLINE JUDGE */
#define WOULD
#define YOU
#define PLEASE
#define ACCEPT
#define MY
#define SUBMISSION
/* I REALLY HOPE MY WISH REACH YOU , ATCODER'S ONLINE JUDGE */
#include <algorithm> // min, max, swap, sort, reverse, lower_bound, upper_bound
#include <cstdint>   // int64_t, int*_t
#include <iomanip>
#include <iostream> // cout, endl, cin
#include <limits>   //setprecision
#include <string>   // string, to_string, stoi
#include <tuple>    // tuple, make_tuple
#include <utility>  // pair, make_pair
#include <vector>   // vector
// #include <cstdio> // printf
#include <bitset> // bitset
#include <cmath>  //abs,,,
#include <deque>  // deque
#include <map>    // map
#include <math.h> //pow,,,
#include <queue>  // queue, priority_queue
#include <set>    // set
#include <stack>  // stack
// It is so troublesome that I include bits/stdc++.h !
using namespace std;

template <class T> inline bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
template <class T> inline bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
const long long INF = 100100100100;
const long long MOD = 1000000007;
typedef pair<int, int> P;
// NのM乗を求める(繰り返し二乗法)
long long mod_pow(long long N, long long M) {
  if (M == 0)
    return 1;
  long long res = mod_pow((N * N) % MOD, M / 2);
  // 最下位ビット(*N)が1の時は単独でNをかける
  if (M & 1)
    res = (res * N) % MOD;

  return res %= MOD;
}
long long nCr(long long n, long long r) {
  long long A = 1, B = 1;
  // Aが分子Bが1/r!
  for (long long i = n - r + 1; i <= n; i++) {
    A = A * i % MOD;
  }
  for (long long i = 1; i <= r; i++) {
    B = B * i % MOD;
  }
  B = mod_pow(B, MOD - 2);
  B %= MOD;
  // Bは割るのではなく掛ける
  return (A * B) % MOD;
}

long long gcd(long long a, long long b) {
  if (b == 0)
    return a;
  else
    return gcd(b, a % b);
}

long long lcm(long long a, long long b) { return a * b / gcd(a, b); }

// long long A,B;
bool ok(long long key, long long index) {
  if (index > key)
    return true;
  else if (index <= key)
    return false;
}
long long binary_search(long long key, long long size) {
  // left,right,midはいずれもindex
  long long left = -1, right = size;
  while (right - left > 1) {
    long long mid = left + (right - left) / 2;
    long long hantei = ok(key, mid);
    if (hantei)
      right = mid;
    else
      left = mid;
  }
  if (left == -1)
    return 0;
  return left;
}

int main() {
  long long N, K;
  cin >> N >> K;
  vector<long long> retu(N);
  for (long long i = 0; i < N; i++)
    cin >> retu.at(i);
  vector<long long> ato;
  set<long long> S;
  long long count = 0;
  long long now = 1;
  bool ok = false;
  if (N >= K)
    ok = true;
  while (true) {
    S.insert(now);
    count++;
    if (count != S.size() && !ok) {
      // now = retu.at(now-1);
      break;
    }
    if (ok && count == K) {
      cout << retu.at(now - 1) << endl;
      return 0;
    }
    ato.push_back(now);
    now = retu.at(now - 1);
  }
  long long last = now;
  // cout << last << endl;
  long long musi = 0;
  // for(int i = 0;i<ato.size();i++) cout << ato.at(i) << endl;
  for (long long i = 0; i < ato.size(); i++) {
    if (ato.at(i) != last)
      musi++;
    else
      break;
  }
  K -= musi;
  long long amari = K % (ato.size() - musi);
  // cout << amari << endl;
  cout << ato.at(amari + musi) << endl;
}


Error: 0

Fixed submission:

/*~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=
*$* WRITER:kakitamasziru/OxOmisosiru *$*
~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=~=*/
#ifdef LOCAL_JUDGE
#define _GLIBCXX_DEBUG // FOR THE DEBUG! COMMENT OUT THIS WHEN SUBMITTING!
#endif
/* I REALLY HOPE MY WISH REACH YOU , ATCODER'S ONLINE JUDGE */
#define WOULD
#define YOU
#define PLEASE
#define ACCEPT
#define MY
#define SUBMISSION
/* I REALLY HOPE MY WISH REACH YOU , ATCODER'S ONLINE JUDGE */
#include <algorithm> // min, max, swap, sort, reverse, lower_bound, upper_bound
#include <cstdint>   // int64_t, int*_t
#include <iomanip>
#include <iostream> // cout, endl, cin
#include <limits>   //setprecision
#include <string>   // string, to_string, stoi
#include <tuple>    // tuple, make_tuple
#include <utility>  // pair, make_pair
#include <vector>   // vector
// #include <cstdio> // printf
#include <bitset> // bitset
#include <cmath>  //abs,,,
#include <deque>  // deque
#include <map>    // map
#include <math.h> //pow,,,
#include <queue>  // queue, priority_queue
#include <set>    // set
#include <stack>  // stack
// It is so troublesome that I include bits/stdc++.h !
using namespace std;

template <class T> inline bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
template <class T> inline bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
const long long INF = 100100100100;
const long long MOD = 1000000007;
typedef pair<int, int> P;
// NのM乗を求める(繰り返し二乗法)
long long mod_pow(long long N, long long M) {
  if (M == 0)
    return 1;
  long long res = mod_pow((N * N) % MOD, M / 2);
  // 最下位ビット(*N)が1の時は単独でNをかける
  if (M & 1)
    res = (res * N) % MOD;

  return res %= MOD;
}
long long nCr(long long n, long long r) {
  long long A = 1, B = 1;
  // Aが分子Bが1/r!
  for (long long i = n - r + 1; i <= n; i++) {
    A = A * i % MOD;
  }
  for (long long i = 1; i <= r; i++) {
    B = B * i % MOD;
  }
  B = mod_pow(B, MOD - 2);
  B %= MOD;
  // Bは割るのではなく掛ける
  return (A * B) % MOD;
}

long long gcd(long long a, long long b) {
  if (b == 0)
    return a;
  else
    return gcd(b, a % b);
}

long long lcm(long long a, long long b) { return a * b / gcd(a, b); }

// long long A,B;
bool ok(long long key, long long index) {
  if (index > key)
    return true;
  else if (index <= key)
    return false;
}
long long binary_search(long long key, long long size) {
  // left,right,midはいずれもindex
  long long left = -1, right = size;
  while (right - left > 1) {
    long long mid = left + (right - left) / 2;
    long long hantei = ok(key, mid);
    if (hantei)
      right = mid;
    else
      left = mid;
  }
  if (left == -1)
    return 0;
  return left;
}

int main() {
  long long N, K;
  cin >> N >> K;
  vector<int> retu(N);
  for (int i = 0; i < N; i++)
    cin >> retu.at(i);
  vector<int> ato;
  set<int> S;
  int count = 0;
  int now = retu.at(0) - 1;
  while (true) {
    count++;
    S.insert(retu.at(now));
    if (S.size() != count) {
      break;
    }
    ato.push_back(retu.at(now));
    now = retu.at(now) - 1;
  }
  long long A = S.size();
  K--;
  long long amari = K % A;
  /*for(int i = 0;i<ato.size();i++){
      cout << ato.at(i) << " ";
  }
  cout << endl;
  cout << amari << endl;*/
  cout << ato.at(amari - 1) << endl;
}