Problem p02719 (C++) — buggy submission, verdict: Time Limit Exceeded

// template version 1.15
using namespace std;
#include <bits/stdc++.h>

// varibable settings
#define int long long
const int INF = 1e18;

// define basic macro {{{
#define _overload3(_1, _2, _3, name, ...) name
#define _rep(i, n) repi(i, 0, n)
#define repi(i, a, b) for (int i = (int)(a); i < (int)(b); ++i)
#define rep(...) _overload3(__VA_ARGS__, repi, _rep, )(__VA_ARGS__)
#define _rrep(i, n) rrepi(i, 0, n)
#define rrepi(i, a, b) for (int i = (int)((b)-1); i >= (int)(a); --i)
#define rrep(...) _overload3(__VA_ARGS__, rrepi, _rrep, )(__VA_ARGS__)
#define each(i, a) for (auto &&i : a)
#define all(x) (x).begin(), (x).end()
#define sz(x) ((int)(x).size())
#define pb(a) push_back(a)
#define mp(a, b) make_pair(a, b)
#define mt(a, b, c) make_tuple(a, b, c)
#define ub upper_bound
#define lb lower_bound
#define posl(A, x) (lower_bound(all(A), x) - A.begin())
#define posu(A, x) (upper_bound(all(A), x) - A.begin())
template <class T> inline void chmax(T &a, const T &b) {
  if ((a) < (b))
    (a) = (b);
}
template <class T> inline void chmin(T &a, const T &b) {
  if ((a) > (b))
    (a) = (b);
}

#define divceil(a, b) ((a) + (b)-1) / (b)
#define is_in(x, a, b) ((a) <= (x) && (x) < (b))
#define uni(x)                                                                 \\
  sort(all(x));                                                                \\
  x.erase(unique(all(x)), x.end())
#define slice(l, r) substr(l, r - l)

typedef long long ll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef long double ld;
typedef pair<int, int> pii;
typedef tuple<int, int, int> iii;

template <typename T> using PQ = priority_queue<T, vector<T>, greater<T>>;
struct Fast {
  Fast() {
    std::cin.tie(0);
    ios::sync_with_stdio(false);
  }
} fast;

#if defined(PCM) || defined(LOCAL)
#include "lib/dump.hpp"
#else
#define dump(...) 42
#define dump_1d(...) 42
#define dump_2d(...) 42
#define cerrendl 42
#endif
//}}}

signed main() {
  int x, k;
  cin >> x >> k;

  set<int> st;
  st.insert(x);
  int ans = x;
  while (true) {
    if (x > k)
      x %= k;
    else
      x = abs(x - k);
    chmin(ans, x);
    dump(x);
    if (st.find(x) != st.end())
      break;
    else
      st.insert(x);
  }
  cout << ans << endl;

  return 0;
}


Error: TLE

Fixed submission:

// template version 1.15
using namespace std;
#include <bits/stdc++.h>

// varibable settings
#define int long long
const int INF = 1e18;

// define basic macro {{{
#define _overload3(_1, _2, _3, name, ...) name
#define _rep(i, n) repi(i, 0, n)
#define repi(i, a, b) for (int i = (int)(a); i < (int)(b); ++i)
#define rep(...) _overload3(__VA_ARGS__, repi, _rep, )(__VA_ARGS__)
#define _rrep(i, n) rrepi(i, 0, n)
#define rrepi(i, a, b) for (int i = (int)((b)-1); i >= (int)(a); --i)
#define rrep(...) _overload3(__VA_ARGS__, rrepi, _rrep, )(__VA_ARGS__)
#define each(i, a) for (auto &&i : a)
#define all(x) (x).begin(), (x).end()
#define sz(x) ((int)(x).size())
#define pb(a) push_back(a)
#define mp(a, b) make_pair(a, b)
#define mt(a, b, c) make_tuple(a, b, c)
#define ub upper_bound
#define lb lower_bound
#define posl(A, x) (lower_bound(all(A), x) - A.begin())
#define posu(A, x) (upper_bound(all(A), x) - A.begin())
template <class T> inline void chmax(T &a, const T &b) {
  if ((a) < (b))
    (a) = (b);
}
template <class T> inline void chmin(T &a, const T &b) {
  if ((a) > (b))
    (a) = (b);
}

#define divceil(a, b) ((a) + (b)-1) / (b)
#define is_in(x, a, b) ((a) <= (x) && (x) < (b))
#define uni(x)                                                                 \\
  sort(all(x));                                                                \\
  x.erase(unique(all(x)), x.end())
#define slice(l, r) substr(l, r - l)

typedef long long ll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef long double ld;
typedef pair<int, int> pii;
typedef tuple<int, int, int> iii;

template <typename T> using PQ = priority_queue<T, vector<T>, greater<T>>;
struct Fast {
  Fast() {
    std::cin.tie(0);
    ios::sync_with_stdio(false);
  }
} fast;

#if defined(PCM) || defined(LOCAL)
#include "lib/dump.hpp"
#else
#define dump(...) 42
#define dump_1d(...) 42
#define dump_2d(...) 42
#define cerrendl 42
#endif
//}}}

signed main() {
  int x, k;
  cin >> x >> k;

  set<int> st;
  int ans = x;
  while (true) {
    x = abs(x - k);
    chmin(ans, x);
    dump(x);
    if (st.find(x) != st.end())
      break;
    else
      st.insert(x);
  }
  cout << ans << endl;

  return 0;
}