Problem p02596 (C++) — buggy submission, verdict: Time Limit Exceeded

#include <bits/stdc++.h>
using namespace std;
typedef long long int ll;
#define mod 1000000007
#define inf 9000000000000000000
typedef pair<ll, ll> pll;
typedef pair<int, int> pint;
#define PI 3.14159265359
#define endl '\\n'
#define itn int
#define mapint_iterator map<int, int>::iterator
#define mapll_iterator map<ll, ll>::iterator
#define setint_iterator set<int>::iterator
#define setll_iterator set<ll>::iterator
#define setpint_iterator set<pint>::iterator
#define setpll_iterator set<pll>::iterator
#define cout1(a) cout << a << endl
#define cout2(a, b) cout << a << ' ' << b << endl
#define cout3(a, b, c) cout << a << " " << b << " " << c << endl
#define cout4(a, b, c, d) cout << a << " " << b << " " << c << " " << d << endl
#define vcout(v, i) cout << v[i].fi << " " << v[i].se << endl
typedef priority_queue<pair<pll, pll>, vector<pair<pll, pll>>,
                       greater<pair<pll, pll>>>
    pqset;
typedef priority_queue<pll, vector<pll>, greater<pll>> pqset_ll;
#define pb push_back
#define pf push_front
#define fi first
#define mkp make_pair
#define se second
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
typedef tree<int, null_type, less<int>, rb_tree_tag,
             tree_order_statistics_node_update>
    os;
typedef tree<pll, null_type, less<pll>, rb_tree_tag,
             tree_order_statistics_node_update>
    os_pair;
#define rep(i, n) for (ll i = 0; i < n; i++)
#define repeat(i, start, n) for (ll i = start; i < n; i++)
#define FileIO                                                                 \\
  freopen("input.txt", "r", stdin);                                            \\
  freopen("output.txt", "w", stdout)
ll ll_max(ll a, ll b, ll c) { return max(a, max(b, c)); }
int int_max(int a, int b, int c) { return max(a, max(b, c)); }
ll ll_min(ll a, ll b, ll c) { return min(a, min(b, c)); }
int int_min(int a, int b, int c) { return min(a, min(b, c)); }
ll max(int a, ll b) { return max((ll)a, b); }
ll min(int a, ll b) { return min((ll)a, b); }
ll min(ll a, int b) { return min(a, (ll)b); }
ll max(ll a, int b) { return max(a, (ll)b); }
ll power(ll a, ll b) {
  if (a == 1)
    return 1;
  if (b == 0)
    return 1;
  ll c = power(a, b / 2);
  ll res = 1;
  if (b % 2) {
    res = c * c;
    if (res >= mod)
      res %= mod;
    res *= a;
  } else
    res = c * c;
  if (res >= mod)
    res %= mod;
  return res;
}
ll power(ll a, ll b, ll mod1) {
  if (a == 1)
    return 1;
  if (b == 0)
    return 1;
  ll c = power(a, b / 2, mod1);
  ll res = 1;
  if (b % 2) {
    res = c * c;
    if (res >= mod1)
      res %= mod1;
    res *= a;
  } else
    res = c * c;
  if (res >= mod1)
    res %= mod1;
  return res;
}
ll modInv(ll a) { return power(a, mod - 2); }
ll fact[1], inv[1];
void factorial(ll n) {
  fact[0] = 1;
  for (ll i = 1; i <= n; i++) {
    fact[i] = fact[i - 1] * i;
    if (fact[i] >= mod)
      fact[i] %= mod;
  }
}
void InvFactorial(ll n) {
  inv[0] = 1;
  for (ll i = 1; i <= n; i++)
    inv[i] = modInv(fact[i]);
}
ll ncr(ll n, ll r) {
  if (n < r || n < 0 || r < 0)
    return 0;
  ll b = inv[n - r];
  ll c = inv[r];
  ll a = fact[n] * b;
  if (a >= mod)
    a %= mod;
  a *= c;
  if (a >= mod)
    a %= mod;
  return a;
}
bool prime[1];
vector<ll> primes;
void remove_duplicates(vector<pair<int, pint>> &v) {
  sort(v.begin(), v.end());
  int _size = unique(v.begin(), v.end()) - v.begin();
  v.resize(_size);
}
ll gcdll(ll u, ll v) {
  ll shift;
  if (u == 0)
    return v;
  if (v == 0)
    return u;
  shift = __builtin_ctzll(u | v);
  u >>= __builtin_ctzll(u);
  do {
    v >>= __builtin_ctzll(v);
    if (u > v) {
      ll t = v;
      v = u;
      u = t;
    }
    v = v - u;
  } while (v != 0);
  return u << shift;
}
unsigned int gcd(unsigned int u, unsigned int v) {
  unsigned int shift;
  if (u == 0)
    return v;
  if (v == 0)
    return u;
  shift = __builtin_ctz(u | v);
  u >>= __builtin_ctz(u);
  do {
    v >>= __builtin_ctz(v);
    if (u > v) {
      unsigned int t = v;
      v = u;
      u = t;
    }
    v = v - u;
  } while (v != 0);
  return u << shift;
}
void sieve(ll n) {
  memset(prime, true, sizeof(prime));
  prime[1] = false;
  for (ll p = 2; p * p <= n; p++) {
    if (prime[p]) {
      for (ll i = p * p; i <= n; i += p)
        prime[i] = false;
    }
  }
  repeat(i, 2, n + 1) if (prime[i]) primes.pb(i);
}
// freopen("input.txt","r",stdin);freopen("output.txt","w",stdout)
// Use (<<) for multiplication
// Use (>>) for division
//  find_by_order -> value at index
//  order_of_key -> index of value
//  in Floyd-Warshall Algo, k is outer loop
//__gcd(0,0) gives runtime error
// power(a,b) == power(a,b%phi(a)) Fermet's Theorem
// never use "=" operator in compare function
// For checking odd cycles, check bipartite
// Range in iterative segment tree [a,b)
//  no of prime numbers in range : (70,19) , (1000,168) , (100000,1229) ,
//  (sqrt(10^9),3409) ;
void solve(int countu) {
  ll k;
  cin >> k;
  if (k % 7 == 0)
    k /= 7;
  if (k % 2 == 0) {
    cout1(-1);
    return;
  }
  if (k == 1) {
    cout1(1);
    return;
  }
  ll start = 1;
  int count = 1;
  ll mul = 10;
  while (start) {
    start += mul;
    start %= k;
    if (start == 0) {
      cout1(count + 1);
      return;
    }
    mul *= 10;
    mul %= k;
    count++;
    if (count > k) {
      cout1(-1);
      return;
    }
  }
}
int main() {
  // freopen("input.txt","r",stdin);freopen("output.txt","w",stdout);
  cin.tie(NULL);
  cout.tie(NULL);
  cin.sync_with_stdio(0);
  cout.sync_with_stdio(0);
  cout << fixed;
  srand(time(0));
  // cout.precision(9);
  int t = 1;
  // cin>>t;
  int countu = 1;
  for (int i = 1; i <= t; i++) {
    solve(countu);
    countu++;
  }
}

Error: TLE

Fixed submission:

#include <bits/stdc++.h>
using namespace std;
typedef long long int ll;
#define mod 1000000007
#define inf 9000000000000000000
typedef pair<ll, ll> pll;
typedef pair<int, int> pint;
#define PI 3.14159265359
#define endl '\\n'
#define itn int
#define mapint_iterator map<int, int>::iterator
#define mapll_iterator map<ll, ll>::iterator
#define setint_iterator set<int>::iterator
#define setll_iterator set<ll>::iterator
#define setpint_iterator set<pint>::iterator
#define setpll_iterator set<pll>::iterator
#define cout1(a) cout << a << endl
#define cout2(a, b) cout << a << ' ' << b << endl
#define cout3(a, b, c) cout << a << " " << b << " " << c << endl
#define cout4(a, b, c, d) cout << a << " " << b << " " << c << " " << d << endl
#define vcout(v, i) cout << v[i].fi << " " << v[i].se << endl
typedef priority_queue<pair<pll, pll>, vector<pair<pll, pll>>,
                       greater<pair<pll, pll>>>
    pqset;
typedef priority_queue<pll, vector<pll>, greater<pll>> pqset_ll;
#define pb push_back
#define pf push_front
#define fi first
#define mkp make_pair
#define se second
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
typedef tree<int, null_type, less<int>, rb_tree_tag,
             tree_order_statistics_node_update>
    os;
typedef tree<pll, null_type, less<pll>, rb_tree_tag,
             tree_order_statistics_node_update>
    os_pair;
#define rep(i, n) for (ll i = 0; i < n; i++)
#define repeat(i, start, n) for (ll i = start; i < n; i++)
#define FileIO                                                                 \\
  freopen("input.txt", "r", stdin);                                            \\
  freopen("output.txt", "w", stdout)
ll ll_max(ll a, ll b, ll c) { return max(a, max(b, c)); }
int int_max(int a, int b, int c) { return max(a, max(b, c)); }
ll ll_min(ll a, ll b, ll c) { return min(a, min(b, c)); }
int int_min(int a, int b, int c) { return min(a, min(b, c)); }
ll max(int a, ll b) { return max((ll)a, b); }
ll min(int a, ll b) { return min((ll)a, b); }
ll min(ll a, int b) { return min(a, (ll)b); }
ll max(ll a, int b) { return max(a, (ll)b); }
ll power(ll a, ll b) {
  if (a == 1)
    return 1;
  if (b == 0)
    return 1;
  ll c = power(a, b / 2);
  ll res = 1;
  if (b % 2) {
    res = c * c;
    if (res >= mod)
      res %= mod;
    res *= a;
  } else
    res = c * c;
  if (res >= mod)
    res %= mod;
  return res;
}
ll power(ll a, ll b, ll mod1) {
  if (a == 1)
    return 1;
  if (b == 0)
    return 1;
  ll c = power(a, b / 2, mod1);
  ll res = 1;
  if (b % 2) {
    res = c * c;
    if (res >= mod1)
      res %= mod1;
    res *= a;
  } else
    res = c * c;
  if (res >= mod1)
    res %= mod1;
  return res;
}
ll modInv(ll a) { return power(a, mod - 2); }
ll fact[1], inv[1];
void factorial(ll n) {
  fact[0] = 1;
  for (ll i = 1; i <= n; i++) {
    fact[i] = fact[i - 1] * i;
    if (fact[i] >= mod)
      fact[i] %= mod;
  }
}
void InvFactorial(ll n) {
  inv[0] = 1;
  for (ll i = 1; i <= n; i++)
    inv[i] = modInv(fact[i]);
}
ll ncr(ll n, ll r) {
  if (n < r || n < 0 || r < 0)
    return 0;
  ll b = inv[n - r];
  ll c = inv[r];
  ll a = fact[n] * b;
  if (a >= mod)
    a %= mod;
  a *= c;
  if (a >= mod)
    a %= mod;
  return a;
}
bool prime[1];
vector<ll> primes;
void remove_duplicates(vector<pair<int, pint>> &v) {
  sort(v.begin(), v.end());
  int _size = unique(v.begin(), v.end()) - v.begin();
  v.resize(_size);
}
ll gcdll(ll u, ll v) {
  ll shift;
  if (u == 0)
    return v;
  if (v == 0)
    return u;
  shift = __builtin_ctzll(u | v);
  u >>= __builtin_ctzll(u);
  do {
    v >>= __builtin_ctzll(v);
    if (u > v) {
      ll t = v;
      v = u;
      u = t;
    }
    v = v - u;
  } while (v != 0);
  return u << shift;
}
unsigned int gcd(unsigned int u, unsigned int v) {
  unsigned int shift;
  if (u == 0)
    return v;
  if (v == 0)
    return u;
  shift = __builtin_ctz(u | v);
  u >>= __builtin_ctz(u);
  do {
    v >>= __builtin_ctz(v);
    if (u > v) {
      unsigned int t = v;
      v = u;
      u = t;
    }
    v = v - u;
  } while (v != 0);
  return u << shift;
}
void sieve(ll n) {
  memset(prime, true, sizeof(prime));
  prime[1] = false;
  for (ll p = 2; p * p <= n; p++) {
    if (prime[p]) {
      for (ll i = p * p; i <= n; i += p)
        prime[i] = false;
    }
  }
  repeat(i, 2, n + 1) if (prime[i]) primes.pb(i);
}
// freopen("input.txt","r",stdin);freopen("output.txt","w",stdout)
// Use (<<) for multiplication
// Use (>>) for division
//  find_by_order -> value at index
//  order_of_key -> index of value
//  in Floyd-Warshall Algo, k is outer loop
//__gcd(0,0) gives runtime error
// power(a,b) == power(a,b%phi(a)) Fermet's Theorem
// never use "=" operator in compare function
// For checking odd cycles, check bipartite
// Range in iterative segment tree [a,b)
//  no of prime numbers in range : (70,19) , (1000,168) , (100000,1229) ,
//  (sqrt(10^9),3409) ;
void solve(int countu) {
  ll k;
  cin >> k;
  if (k % 7 == 0)
    k /= 7;
  if (k % 2 == 0) {
    cout1(-1);
    return;
  }
  if (k == 1) {
    cout1(1);
    return;
  }
  ll start = 1;
  int count = 1;
  while (start) {
    start += power(10, count, k);
    start %= k;
    if (start == 0) {
      cout1(count + 1);
      return;
    }
    count++;
  }
}
int main() {
  // freopen("input.txt","r",stdin);freopen("output.txt","w",stdout);
  cin.tie(NULL);
  cout.tie(NULL);
  cin.sync_with_stdio(0);
  cout.sync_with_stdio(0);
  cout << fixed;
  srand(time(0));
  // cout.precision(9);
  int t = 1;
  // cin>>t;
  int countu = 1;
  for (int i = 1; i <= t; i++) {
    solve(countu);
    countu++;
  }
}