Problem p00687 (C++) — buggy submission, verdict: Time Limit Exceeded

////////////////////////////////////////
///  tu3 pro-con template            ///
////////////////////////////////////////
#include <algorithm>
#include <bitset>
#include <cassert>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstring>
#include <functional>
#include <iostream>
#include <list>
#include <map>
#include <numeric>
#include <queue>
#include <regex>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <vector>
using namespace std;

//// MACRO ////
#define countof(a) (sizeof(a) / sizeof(a[0]))

#define REP(i, n) for (int i = 0; i < (n); i++)
#define RREP(i, n) for (int i = (n)-1; i >= 0; i--)
#define FOR(i, s, n) for (int i = (s); i < (n); i++)
#define RFOR(i, s, n) for (int i = (n)-1; i >= (s); i--)
#define pos(c, i) c.being() + (i)
#define allof(c) c.begin(), c.end()
#define aallof(a) a, countof(a)
#define partof(c, i, n) c.begin() + (i), c.begin() + (i) + (n)
#define apartof(a, i, n) a + (i), a + (i) + (n)

#define EPS 1e-9
#define INF (1L << 30)
#define LINF (1LL << 60)

inline int sign(double x) { return (abs(x) < EPS ? 0 : x > 0 ? 1 : -1); }

//// i/o helper ////

struct _Reader {
  template <class T> _Reader operator,(T &rhs) {
    cin >> rhs;
    return *this;
  }
};
struct _Writer {
  bool f;
  _Writer() : f(false) {}
  template <class T> _Writer operator,(const T &rhs) {
    cout << (f ? " " : "") << rhs;
    f = true;
    return *this;
  }
};
#define READ(t, ...)                                                           \\
  t __VA_ARGS__;                                                               \\
  _Reader(), __VA_ARGS__
#define WRITE(...)                                                             \\
  _Writer(), __VA_ARGS__;                                                      \\
  cout << endl

//// start up ////
void solve();
int main() {
  solve();
  return 0;
}

////////////////////
/// template end ///
////////////////////
#define long long long

// 最大公約数
long gcd(long a, long b) { return b ? gcd(b, a % b) : a; }

// 最小公倍数
long lcm(long a, long b) { return a / gcd(a, b) * b; }

void solve() {
  int cases = INF;
  REP(_, cases) {
    READ(int, n, a, b);
    if (!(n | a | b)) {
      break;
    }
    if (a > b)
      swap(a, b);
    vector<char> m(n + 1);

    int maxJ = lcm(a, b) / b;

    for (int i = 0; a * i <= n; i++) {
      for (int j = 0; a * i + b * j <= n && j < maxJ; j++) {
        m[a * i + b * j] = 1;
      }
    }
    WRITE(n + 1 - count(allof(m), 1));
  }
}

Error: TLE

Fixed submission:

////////////////////////////////////////
///  tu3 pro-con template            ///
////////////////////////////////////////
#include <algorithm>
#include <bitset>
#include <cassert>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstring>
#include <functional>
#include <iostream>
#include <list>
#include <map>
#include <numeric>
#include <queue>
#include <regex>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <vector>
using namespace std;

//// MACRO ////
#define countof(a) (sizeof(a) / sizeof(a[0]))

#define REP(i, n) for (int i = 0; i < (n); i++)
#define RREP(i, n) for (int i = (n)-1; i >= 0; i--)
#define FOR(i, s, n) for (int i = (s); i < (n); i++)
#define RFOR(i, s, n) for (int i = (n)-1; i >= (s); i--)
#define pos(c, i) c.being() + (i)
#define allof(c) c.begin(), c.end()
#define aallof(a) a, countof(a)
#define partof(c, i, n) c.begin() + (i), c.begin() + (i) + (n)
#define apartof(a, i, n) a + (i), a + (i) + (n)

#define EPS 1e-9
#define INF (1L << 30)
#define LINF (1LL << 60)

inline int sign(double x) { return (abs(x) < EPS ? 0 : x > 0 ? 1 : -1); }

//// i/o helper ////

struct _Reader {
  template <class T> _Reader operator,(T &rhs) {
    cin >> rhs;
    return *this;
  }
};
struct _Writer {
  bool f;
  _Writer() : f(false) {}
  template <class T> _Writer operator,(const T &rhs) {
    cout << (f ? " " : "") << rhs;
    f = true;
    return *this;
  }
};
#define READ(t, ...)                                                           \\
  t __VA_ARGS__;                                                               \\
  _Reader(), __VA_ARGS__
#define WRITE(...)                                                             \\
  _Writer(), __VA_ARGS__;                                                      \\
  cout << endl

//// start up ////
void solve();
int main() {
  solve();
  return 0;
}

////////////////////
/// template end ///
////////////////////

void solve() {
  int cases = INF;
  REP(_, cases) {
    READ(int, n, a, b);
    if (!(n | a | b)) {
      break;
    }
    vector<char> m(n + 1);
    REP(i, n / a + 1)
    REP(j, (n - a * i) / b + 1)
    m[a * i + b * j] = 1;
    WRITE(n + 1 - count(allof(m), 1));
  }
}