Problem p02596 (C++) — buggy submission, verdict: Runtime Error

/*
            _           __                _      _____ _____ _____
  ___ _   _| |__   ___ / _|_ __ ___  __ _| | __ |___  |___  |___  |
 / __| | | | '_ \\ / _ \\ |_| '__/ _ \\/ _` | |/ /    / /   / /   / /
| (__| |_| | |_) |  __/  _| | |  __/ (_| |   <    / /   / /   / /
 \\___|\\__,_|_.__/ \\___|_| |_|  \\___|\\__,_|_|\\_\\  /_/   /_/   /_/

*/
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
#define CS custom_hash
#define vi vector
#define loop(i, a, b) for (ll i = a; i < b; i++)
#define For(i, n) for (int i = 0; i < (ll)n; i++)
#define Rev(i, n) for (int i = n - 1; i >= 0; i--)
#define Rep(i, n) for (int i = 1; i <= n; ++i)
#define F first
#define S second
#define pb push_back
#define em emplace_back
#define all(v) (v).begin(), (v).end()
#define mems(x, y) memset(x, y, sizeof(x))
#define sz(x) (int)(x).size()
#define mp(a, b) make_pair(a, b)
#define po(n) cout << n << "\\n "
#define ar array
#define endl "\\n"
#define PI acos(-1)
#define umap unordered_map
#define gmap gp_hash_table
void __print(int x) { cerr << x; }
void __print(long x) { cerr << x; }
void __print(long long x) { cerr << x; }
void __print(unsigned x) { cerr << x; }
void __print(unsigned long x) { cerr << x; }
void __print(unsigned long long x) { cerr << x; }
void __print(float x) { cerr << x; }
void __print(double x) { cerr << x; }
void __print(long double x) { cerr << x; }
void __print(char x) { cerr << '\\'' << x << '\\''; }
void __print(const char *x) { cerr << '\\"' << x << '\\"'; }
void __print(const string &x) { cerr << '\\"' << x << '\\"'; }
void __print(bool x) { cerr << (x ? "true" : "false"); }
template <typename T, typename V> void __print(const pair<T, V> &x) {
  cerr << '{';
  __print(x.first);
  cerr << ',';
  __print(x.second);
  cerr << '}';
}
template <typename T> void __print(const T &x) {
  int f = 0;
  cerr << '{';
  for (auto &i : x)
    cerr << (f++ ? "," : ""), __print(i);
  cerr << "}";
}
void _print() { cerr << "]\\n"; }
template <typename T, typename... V> void _print(T t, V... v) {
  __print(t);
  if (sizeof...(v))
    cerr << ", ";
  _print(v...);
}
template <typename T, typename V> void mdebug(map<T, vi<V>> m) {
  for (auto x : m) {
    cerr << x.F << " : [ ";
    for (auto c : x.S)
      cerr << c << " ";
    cerr << "]" << endl;
  }
}
#define debug(x...)                                                            \\
  cerr << "[" << #x << "] = [";                                                \\
  _print(x)
// #ifndef ONLINE_JUDGE
// #ifndef LOCAL
#define debug(x...)                                                            \\
  cerr << "[" << #x << "] = [";                                                \\
  _print(x)
// #else
// #define debug(x...)
// #endif
// #pragma GCC optimize "trapv"
template <class T>
using oset =
    tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
// credits for below template:William Lin(tmwilliamlin168)
#define F_OR(i, a, b, s)                                                       \\
  for (int i = (a); ((s) > 0 ? i < (b) : i > (b)); i += (s))
#define F_OR1(e) F_OR(i, 0, e, 1)
#define F_OR2(i, e) F_OR(i, 0, e, 1)
#define F_OR3(i, b, e) F_OR(i, b, e, 1)
#define F_OR4(i, b, e, s) F_OR(i, b, e, s)
#define GET5(a, b, c, d, e, ...) e
#define F_ORC(...) GET5(__VA_ARGS__, F_OR4, F_OR3, F_OR2, F_OR1)
#define FOR(...) F_ORC(__VA_ARGS__)(__VA_ARGS__)
#define EACH(x, a) for (auto &x : a)
template <class A> void read(vi<A> &v);
template <class A, size_t S> void read(ar<A, S> &a);
template <class T> void read(T &x) { cin >> x; }
void read(double &d) {
  string t;
  read(t);
  d = stod(t);
}
void read(long double &d) {
  string t;
  read(t);
  d = stold(t);
}
template <class H, class... T> void read(H &h, T &...t) {
  read(h);
  read(t...);
}
template <class A> void read(vi<A> &x) {
  EACH(a, x)
  read(a);
}
template <class A, size_t S> void read(array<A, S> &x) {
  EACH(a, x)
  read(a);
}
string to_string(char c) { return string(1, c); }
string to_string(bool b) { return b ? "true" : "false"; }
string to_string(const char *s) { return string(s); }
string to_string(string s) { return s; }
string to_string(vi<bool> v) {
  string res;
  FOR(sz(v))
  res += char('0' + v[i]);
  return res;
}

template <size_t S> string to_string(bitset<S> b) {
  string res;
  FOR(S)
  res += char('0' + b[i]);
  return res;
}
template <class T> string to_string(T v) {
  bool f = 1;
  string res;
  EACH(x, v) {
    if (!f)
      res += ' ';
    f = 0;
    res += to_string(x);
  }
  return res;
}

template <class A> void pff(A x) { cout << to_string(x); }
template <class H, class... T> void pff(const H &h, const T &...t) {
  pff(h);
  pff(t...);
}
void print() { pff("\\n"); }
template <class H, class... T> void print(const H &h, const T &...t) {
  pff(h);
  if (sizeof...(t))
    pff(' ');
  print(t...);
}
struct PH {
  size_t operator()(const pair<int, int> &x) const {
    size_t ans = 0;
    for (int i = 0; i < x.first; i++)
      ans += x.second;
    return ans;
  }
};
struct custom_hash {
  static uint64_t splitmix64(uint64_t x) {
    // http://xorshift.di.unimi.it/splitmix64.c
    x += 0x9e3779b97f4a7c15;
    x = (x ^ (x >> 30)) * 0xbf58476d1ce4e5b9;
    x = (x ^ (x >> 27)) * 0x94d049bb133111eb;
    return x ^ (x >> 31);
  }
  size_t operator()(uint64_t x) const {
    static const uint64_t FIXED_RANDOM =
        chrono::steady_clock::now().time_since_epoch().count();
    return splitmix64(x + FIXED_RANDOM);
  }
};
// void DBG() {
// 	cerr << "]" << endl;
// }
// template<class H, class... T> void DBG(H h, T... t) {
// 	cerr << to_string(h);
// 	if(sizeof...(t))
// 		cerr << ", ";
// 	DBG(t...);
// }
// // #ifdef _DEBUG
// #define dbg(...) cerr << "LINE(" << __LINE__ << ") -> [" << #__VA_ARGS__ <<
// "]: [", DBG(__VA_ARGS__)
// // #else
// // #define dbg(...) 0
// // #endif

template <class T> void offset(ll o, T &x) { x += o; }
template <class T> void offset(ll o, vi<T> &x) {
  EACH(a, x)
  offset(o, a);
}
template <class T, size_t S> void offset(ll o, ar<T, S> &x) {
  EACH(a, x)
  offset(o, a);
}
#define pf(n) return print(n)
#define int ll
long const M = 1e9 + 7;
const ll INF = 1e18;
// order_of_key (k) : Number of items strictly smaller than k .
// find_by_order(k) : K-th element in a set (counting from zero).
// Syntax to create a min heap for priority queue
// priority_queue <T, vector<T>, greater<T>>pq ;

// make sure to clear the adjacency list for every test case
//  check mxN size
const long mxN = 1e5 + 2;
int countOnes(int n) {
  if (n % 7 == 0)
    n /= 7;
  // to store number of 1s in smallest
  // repunit multiple of the number.
  int count = 1;

  // initialize rem with 1
  int rem = 1 % n;
  // run loop until rem becomes zero
  set<int> s = {rem};
  while (1) {
    if (rem == 0)
      return count;
    rem = (rem * 10 + 1) % n;
    if (s.count(rem))
      return -1;
    s.insert(rem);
    count++;
  }

  // when remainder becomes 0
  // return count
  return count;
}
void solve() {
  int k;
  read(k);
  print(countOnes(k));
}
signed main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  // cout << setprecision(20) << fixed ;
  int T = 1;
  // 	read(T);
  FOR(_, T) {
    // pff("Case #", _+1, ": ");
    solve();
  }
  return 0;
}


Error: WA

Fixed submission:

/*
            _           __                _      _____ _____ _____
  ___ _   _| |__   ___ / _|_ __ ___  __ _| | __ |___  |___  |___  |
 / __| | | | '_ \\ / _ \\ |_| '__/ _ \\/ _` | |/ /    / /   / /   / /
| (__| |_| | |_) |  __/  _| | |  __/ (_| |   <    / /   / /   / /
 \\___|\\__,_|_.__/ \\___|_| |_|  \\___|\\__,_|_|\\_\\  /_/   /_/   /_/

*/
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
#define CS custom_hash
#define vi vector
#define loop(i, a, b) for (ll i = a; i < b; i++)
#define For(i, n) for (int i = 0; i < (ll)n; i++)
#define Rev(i, n) for (int i = n - 1; i >= 0; i--)
#define Rep(i, n) for (int i = 1; i <= n; ++i)
#define F first
#define S second
#define pb push_back
#define em emplace_back
#define all(v) (v).begin(), (v).end()
#define mems(x, y) memset(x, y, sizeof(x))
#define sz(x) (int)(x).size()
#define mp(a, b) make_pair(a, b)
#define po(n) cout << n << "\\n "
#define ar array
#define endl "\\n"
#define PI acos(-1)
#define umap unordered_map
#define gmap gp_hash_table
void __print(int x) { cerr << x; }
void __print(long x) { cerr << x; }
void __print(long long x) { cerr << x; }
void __print(unsigned x) { cerr << x; }
void __print(unsigned long x) { cerr << x; }
void __print(unsigned long long x) { cerr << x; }
void __print(float x) { cerr << x; }
void __print(double x) { cerr << x; }
void __print(long double x) { cerr << x; }
void __print(char x) { cerr << '\\'' << x << '\\''; }
void __print(const char *x) { cerr << '\\"' << x << '\\"'; }
void __print(const string &x) { cerr << '\\"' << x << '\\"'; }
void __print(bool x) { cerr << (x ? "true" : "false"); }
template <typename T, typename V> void __print(const pair<T, V> &x) {
  cerr << '{';
  __print(x.first);
  cerr << ',';
  __print(x.second);
  cerr << '}';
}
template <typename T> void __print(const T &x) {
  int f = 0;
  cerr << '{';
  for (auto &i : x)
    cerr << (f++ ? "," : ""), __print(i);
  cerr << "}";
}
void _print() { cerr << "]\\n"; }
template <typename T, typename... V> void _print(T t, V... v) {
  __print(t);
  if (sizeof...(v))
    cerr << ", ";
  _print(v...);
}
template <typename T, typename V> void mdebug(map<T, vi<V>> m) {
  for (auto x : m) {
    cerr << x.F << " : [ ";
    for (auto c : x.S)
      cerr << c << " ";
    cerr << "]" << endl;
  }
}
#define debug(x...)                                                            \\
  cerr << "[" << #x << "] = [";                                                \\
  _print(x)
// #ifndef ONLINE_JUDGE
// #ifndef LOCAL
#define debug(x...)                                                            \\
  cerr << "[" << #x << "] = [";                                                \\
  _print(x)
// #else
// #define debug(x...)
// #endif
// #pragma GCC optimize "trapv"
template <class T>
using oset =
    tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
// credits for below template:William Lin(tmwilliamlin168)
#define F_OR(i, a, b, s)                                                       \\
  for (int i = (a); ((s) > 0 ? i < (b) : i > (b)); i += (s))
#define F_OR1(e) F_OR(i, 0, e, 1)
#define F_OR2(i, e) F_OR(i, 0, e, 1)
#define F_OR3(i, b, e) F_OR(i, b, e, 1)
#define F_OR4(i, b, e, s) F_OR(i, b, e, s)
#define GET5(a, b, c, d, e, ...) e
#define F_ORC(...) GET5(__VA_ARGS__, F_OR4, F_OR3, F_OR2, F_OR1)
#define FOR(...) F_ORC(__VA_ARGS__)(__VA_ARGS__)
#define EACH(x, a) for (auto &x : a)
template <class A> void read(vi<A> &v);
template <class A, size_t S> void read(ar<A, S> &a);
template <class T> void read(T &x) { cin >> x; }
void read(double &d) {
  string t;
  read(t);
  d = stod(t);
}
void read(long double &d) {
  string t;
  read(t);
  d = stold(t);
}
template <class H, class... T> void read(H &h, T &...t) {
  read(h);
  read(t...);
}
template <class A> void read(vi<A> &x) {
  EACH(a, x)
  read(a);
}
template <class A, size_t S> void read(array<A, S> &x) {
  EACH(a, x)
  read(a);
}
string to_string(char c) { return string(1, c); }
string to_string(bool b) { return b ? "true" : "false"; }
string to_string(const char *s) { return string(s); }
string to_string(string s) { return s; }
string to_string(vi<bool> v) {
  string res;
  FOR(sz(v))
  res += char('0' + v[i]);
  return res;
}

template <size_t S> string to_string(bitset<S> b) {
  string res;
  FOR(S)
  res += char('0' + b[i]);
  return res;
}
template <class T> string to_string(T v) {
  bool f = 1;
  string res;
  EACH(x, v) {
    if (!f)
      res += ' ';
    f = 0;
    res += to_string(x);
  }
  return res;
}

template <class A> void pff(A x) { cout << to_string(x); }
template <class H, class... T> void pff(const H &h, const T &...t) {
  pff(h);
  pff(t...);
}
void print() { pff("\\n"); }
template <class H, class... T> void print(const H &h, const T &...t) {
  pff(h);
  if (sizeof...(t))
    pff(' ');
  print(t...);
}
struct PH {
  size_t operator()(const pair<int, int> &x) const {
    size_t ans = 0;
    for (int i = 0; i < x.first; i++)
      ans += x.second;
    return ans;
  }
};
struct custom_hash {
  static uint64_t splitmix64(uint64_t x) {
    // http://xorshift.di.unimi.it/splitmix64.c
    x += 0x9e3779b97f4a7c15;
    x = (x ^ (x >> 30)) * 0xbf58476d1ce4e5b9;
    x = (x ^ (x >> 27)) * 0x94d049bb133111eb;
    return x ^ (x >> 31);
  }
  size_t operator()(uint64_t x) const {
    static const uint64_t FIXED_RANDOM =
        chrono::steady_clock::now().time_since_epoch().count();
    return splitmix64(x + FIXED_RANDOM);
  }
};
// void DBG() {
// 	cerr << "]" << endl;
// }
// template<class H, class... T> void DBG(H h, T... t) {
// 	cerr << to_string(h);
// 	if(sizeof...(t))
// 		cerr << ", ";
// 	DBG(t...);
// }
// // #ifdef _DEBUG
// #define dbg(...) cerr << "LINE(" << __LINE__ << ") -> [" << #__VA_ARGS__ <<
// "]: [", DBG(__VA_ARGS__)
// // #else
// // #define dbg(...) 0
// // #endif

template <class T> void offset(ll o, T &x) { x += o; }
template <class T> void offset(ll o, vi<T> &x) {
  EACH(a, x)
  offset(o, a);
}
template <class T, size_t S> void offset(ll o, ar<T, S> &x) {
  EACH(a, x)
  offset(o, a);
}
#define pf(n) return print(n)
#define int ll
long const M = 1e9 + 7;
const ll INF = 1e18;
// order_of_key (k) : Number of items strictly smaller than k .
// find_by_order(k) : K-th element in a set (counting from zero).
// Syntax to create a min heap for priority queue
// priority_queue <T, vector<T>, greater<T>>pq ;

// make sure to clear the adjacency list for every test case
//  check mxN size
const long mxN = 1e5 + 2;
int countOnes(int n) {
  int N = n;
  ;
  int c = 0;
  while (N % 7)
    N /= 7, c++;
  if (c == 1)
    n /= 7;

  // to store number of 1s in smallest
  // repunit multiple of the number.
  int count = 1;

  // initialize rem with 1
  int rem = 1 % n;
  // run loop until rem becomes zero
  set<int> s = {rem};
  while (1) {
    if (rem == 0)
      return count;
    rem = (rem * 10 + 1) % n;
    if (s.count(rem))
      return -1;
    s.insert(rem);
    count++;
  }

  // when remainder becomes 0
  // return count
  return count;
}
void solve() {
  int k;
  read(k);
  print(countOnes(k));
}
signed main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  // cout << setprecision(20) << fixed ;
  int T = 1;
  // 	read(T);
  FOR(_, T) {
    // pff("Case #", _+1, ": ");
    solve();
  }
  return 0;
}