Problem p01268 (C++) — buggy submission, verdict: Time Limit Exceeded

#include <bits/stdc++.h>
using namespace std;
/*{{{*/ // template
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
constexpr int INF = numeric_limits<int>::max() / 2;
constexpr long long LINF = numeric_limits<long long>::max() / 3;
#define mp make_pair
#define pb push_back
#define eb emplace_back
#define fi first
#define se second
#define all(v) (v).begin(), (v).end()
#define sz(x) (int)(x).size()
#define debug(x) cerr << #x << ":" << x << endl
#define debug2(x, y) cerr << #x << "," << #y ":" << x << "," << y << endl
// struct fin{ fin(){ cin.tie(0); ios::sync_with_stdio(false); } } fin_;
struct Double {
  double d;
  explicit Double(double x) : d(x) {}
};
ostream &operator<<(ostream &os, const Double x) {
  os << fixed << setprecision(20) << x.d;
  return os;
}
template <typename T> ostream &operator<<(ostream &os, const vector<T> &vec) {
  os << "[";
  for (const auto &v : vec) {
    os << v << ",";
  }
  os << "]";
  return os;
}
template <typename T, typename U>
ostream &operator<<(ostream &os, const pair<T, U> &p) {
  os << "(" << p.first << "," << p.second << ")";
  return os;
}
template <typename T> ostream &operator<<(ostream &os, const set<T> &st) {
  os << "{";
  for (T v : st)
    os << v << ",";
  os << "}";
  return os;
}
template <typename T, typename U> inline void chmax(T &x, U y) {
  if (y > x)
    x = y;
}
template <typename T, typename U> inline void chmin(T &x, U y) {
  if (y < x)
    x = y;
}
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<vi> vvi;
ll gcd(ll a, ll b) {
  if (b == 0)
    return a;
  else
    return gcd(b, a % b);
}
// constexpr double eps = 1e-14;
constexpr double eps = 1e-10;
constexpr ll mod = 1e9 + 7;
const int dx[] = {1, 0, -1, 0}, dy[] = {0, 1, 0, -1};
/*}}}*/

constexpr int MAX_PR = 250000;

bool is_prime[MAX_PR];
vector<int> primes;

void solve(int N, int P) {
  vector<int> v;

  int idx = upper_bound(all(primes), N) - primes.begin();
  for (int i = idx; i < idx + 100; i++) {
    for (int j = i; j < idx + 100; j++) {
      v.push_back(primes[i] + primes[j]);
    }
  }

  sort(all(v));
  cout << v[P - 1] << endl;
}

int main() {
  // prime
  rep(i, MAX_PR) is_prime[i] = true;
  is_prime[0] = is_prime[1] = false;
  for (int i = 2; i < MAX_PR; i++) {
    if (is_prime[i]) {
      for (int j = 2; i * j < MAX_PR; j++)
        is_prime[i * j] = false;
    }
  }
  for (int i = 2; i < MAX_PR; i++)
    if (is_prime[i])
      primes.push_back(i);

  while (1) {
    int n, p;
    cin >> n >> p;
    if (n == -1 and p == -1)
      break;
    solve(n, p);
  }
}


Error: TLE

Fixed submission:

#include <bits/stdc++.h>
using namespace std;
/*{{{*/ // template
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
constexpr int INF = numeric_limits<int>::max() / 2;
constexpr long long LINF = numeric_limits<long long>::max() / 3;
#define mp make_pair
#define pb push_back
#define eb emplace_back
#define fi first
#define se second
#define all(v) (v).begin(), (v).end()
#define sz(x) (int)(x).size()
#define debug(x) cerr << #x << ":" << x << endl
#define debug2(x, y) cerr << #x << "," << #y ":" << x << "," << y << endl
// struct fin{ fin(){ cin.tie(0); ios::sync_with_stdio(false); } } fin_;
struct Double {
  double d;
  explicit Double(double x) : d(x) {}
};
ostream &operator<<(ostream &os, const Double x) {
  os << fixed << setprecision(20) << x.d;
  return os;
}
template <typename T> ostream &operator<<(ostream &os, const vector<T> &vec) {
  os << "[";
  for (const auto &v : vec) {
    os << v << ",";
  }
  os << "]";
  return os;
}
template <typename T, typename U>
ostream &operator<<(ostream &os, const pair<T, U> &p) {
  os << "(" << p.first << "," << p.second << ")";
  return os;
}
template <typename T> ostream &operator<<(ostream &os, const set<T> &st) {
  os << "{";
  for (T v : st)
    os << v << ",";
  os << "}";
  return os;
}
template <typename T, typename U> inline void chmax(T &x, U y) {
  if (y > x)
    x = y;
}
template <typename T, typename U> inline void chmin(T &x, U y) {
  if (y < x)
    x = y;
}
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<vi> vvi;
ll gcd(ll a, ll b) {
  if (b == 0)
    return a;
  else
    return gcd(b, a % b);
}
// constexpr double eps = 1e-14;
constexpr double eps = 1e-10;
constexpr ll mod = 1e9 + 7;
const int dx[] = {1, 0, -1, 0}, dy[] = {0, 1, 0, -1};
/*}}}*/

constexpr int MAX_PR = 250000;

bool is_prime[MAX_PR];
vector<int> primes;

void solve(int N, int P) {
  vector<int> v;
  int cnt = 0;
  for (int i = 0; i < primes.size(); i++) {
    if (primes[i] <= N)
      continue;
    if (cnt++ == P * 2)
      break;
    for (int j = i; j < primes.size(); j++) {
      if (primes[j] <= N)
        continue;
      v.push_back(primes[i] + primes[j]);
    }
  }
  sort(all(v));
  cout << v[P - 1] << endl;
}

int main() {
  // prime
  rep(i, MAX_PR) is_prime[i] = true;
  is_prime[0] = is_prime[1] = false;
  for (int i = 2; i < MAX_PR; i++) {
    if (is_prime[i]) {
      for (int j = 2; i * j < MAX_PR; j++)
        is_prime[i * j] = false;
    }
  }
  for (int i = 2; i < MAX_PR; i++)
    if (is_prime[i])
      primes.push_back(i);

  while (1) {
    int n, p;
    cin >> n >> p;
    if (n == -1 and p == -1)
      break;
    solve(n, p);
  }
}