Problem p00811 (C++) — buggy submission, verdict: Time Limit Exceeded

#include <algorithm>
#include <cassert>
#include <cfloat>
#include <climits>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstring>
#include <ctime>
#include <deque>
#include <iomanip>
#include <iostream>
#include <limits>
#include <list>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <utility>
#include <vector>
using namespace std;

#define rep(i, a, n) for (int(i) = (a); (i) < (n); (i)++)
#define repq(i, a, n) for (int(i) = (a); (i) <= (n); (i)++)
#define repr(i, a, n) for (int(i) = (a); (i) >= (n); (i)--)
#define all(v) begin(v), end(v)
#define pb(a) push_back(a)
#define fr first
#define sc second
#define INF 2000000000
#define int long long int

#define X real()
#define Y imag()
#define EPS (1e-10)
#define EQ(a, b) (abs((a) - (b)) < EPS)
#define EQV(a, b) (EQ((a).X, (b).X) && EQ((a).Y, (b).Y))
#define LE(n, m) ((n) < (m) + EPS)
#define LEQ(n, m) ((n) <= (m) + EPS)
#define GE(n, m) ((n) + EPS > (m))
#define GEQ(n, m) ((n) + EPS >= (m))

typedef vector<int> VI;
typedef vector<VI> MAT;
typedef pair<int, int> pii;
typedef long long ll;

typedef complex<double> P;
typedef pair<P, P> L;
typedef pair<P, double> C;

int dx[] = {1, -1, 0, 0};
int dy[] = {0, 0, 1, -1};
int const MOD = 1000000007;
ll mod_pow(ll x, ll n) {
  return (!n) ? 1 : (mod_pow((x * x) % MOD, n / 2) * ((n & 1) ? x : 1)) % MOD;
}
int madd(int a, int b) { return (a + b) % MOD; }
int msub(int a, int b) { return (a - b + MOD) % MOD; }
int mmul(int a, int b) { return (a * b) % MOD; }
int minv(int a) { return mod_pow(a, MOD - 2); }
int mdiv(int a, int b) { return mmul(a, minv(b)); }

namespace std {
bool operator<(const P &a, const P &b) {
  return a.X != b.X ? a.X < b.X : a.Y < b.Y;
}
} // namespace std

vector<int> erat(int n) {
  vector<int> primes(n);
  for (int i = 2; i < n; ++i)
    primes[i] = i;
  for (int i = 2; i * i < n; ++i)
    if (primes[i])
      for (int j = i * i; j < n; j += i)
        primes[j] = 0;
  // ?´???°?????????vector???????´?????????´????????\\?????????????????? (0
  // ??§??????????´??????¨??????)
  primes.erase(remove(primes.begin(), primes.end(), 0), primes.end());
  return primes;
}

vector<int> primes;

signed main() {
  primes = erat(100010);
  int m, a, b;
  while (cin >> m >> a >> b, m || a || b) {
    int lim = upper_bound(primes.begin(), primes.end(), m) - primes.begin();
    // printf("debug: lim = %lld\\n", lim);
    int ma = 0, idx_a, idx_b;
    for (int i = 0; primes[i] * primes[i] < primes[lim]; i++) {
      for (int j = i; primes[i] * primes[j] <= m && j < lim; j++) {
        int p = primes[i], q = primes[j];
        if (a * q > b * p)
          break;
        // printf("p = %lld, q = %lld\\n", p, q);
        if (ma < p * q) {
          ma = p * q;
          idx_a = p, idx_b = q;
        }
      }
    }
    printf("%lld %lld\\n", idx_a, idx_b);
  }
  return 0;
}

Error: TLE

Fixed submission:

#include <algorithm>
#include <cassert>
#include <cfloat>
#include <climits>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstring>
#include <ctime>
#include <deque>
#include <iomanip>
#include <iostream>
#include <limits>
#include <list>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <utility>
#include <vector>
using namespace std;

#define rep(i, a, n) for (int(i) = (a); (i) < (n); (i)++)
#define repq(i, a, n) for (int(i) = (a); (i) <= (n); (i)++)
#define repr(i, a, n) for (int(i) = (a); (i) >= (n); (i)--)
#define all(v) begin(v), end(v)
#define pb(a) push_back(a)
#define fr first
#define sc second
#define INF 2000000000
#define int long long int

#define X real()
#define Y imag()
#define EPS (1e-10)
#define EQ(a, b) (abs((a) - (b)) < EPS)
#define EQV(a, b) (EQ((a).X, (b).X) && EQ((a).Y, (b).Y))
#define LE(n, m) ((n) < (m) + EPS)
#define LEQ(n, m) ((n) <= (m) + EPS)
#define GE(n, m) ((n) + EPS > (m))
#define GEQ(n, m) ((n) + EPS >= (m))

typedef vector<int> VI;
typedef vector<VI> MAT;
typedef pair<int, int> pii;
typedef long long ll;

typedef complex<double> P;
typedef pair<P, P> L;
typedef pair<P, double> C;

int dx[] = {1, -1, 0, 0};
int dy[] = {0, 0, 1, -1};
int const MOD = 1000000007;
ll mod_pow(ll x, ll n) {
  return (!n) ? 1 : (mod_pow((x * x) % MOD, n / 2) * ((n & 1) ? x : 1)) % MOD;
}
int madd(int a, int b) { return (a + b) % MOD; }
int msub(int a, int b) { return (a - b + MOD) % MOD; }
int mmul(int a, int b) { return (a * b) % MOD; }
int minv(int a) { return mod_pow(a, MOD - 2); }
int mdiv(int a, int b) { return mmul(a, minv(b)); }

namespace std {
bool operator<(const P &a, const P &b) {
  return a.X != b.X ? a.X < b.X : a.Y < b.Y;
}
} // namespace std

vector<int> erat(int n) {
  vector<int> primes(n);
  for (int i = 2; i < n; ++i)
    primes[i] = i;
  for (int i = 2; i * i < n; ++i)
    if (primes[i])
      for (int j = i * i; j < n; j += i)
        primes[j] = 0;
  // ?´???°?????????vector???????´?????????´????????\\?????????????????? (0
  // ??§??????????´??????¨??????)
  primes.erase(remove(primes.begin(), primes.end(), 0), primes.end());
  return primes;
}

vector<int> primes;

signed main() {
  primes = erat(100010);
  int m, a, b;
  while (cin >> m >> a >> b, m || a || b) {
    int lim = upper_bound(primes.begin(), primes.end(), m) - primes.begin();
    int ma = 0, idx_a, idx_b;
    rep(i, 0, lim) rep(j, i, lim) {
      int p = primes[i], q = primes[j];
      if (a * q > b * p)
        continue;
      if (p * q > m)
        continue;
      if (ma < p * q) {
        ma = p * q;
        idx_a = p, idx_b = q;
      }
    }
    printf("%lld %lld\\n", idx_a, idx_b);
  }
  return 0;
}