Problem p02624 (C++) — buggy submission, verdict: Time Limit Exceeded

#include <bits/stdc++.h>

using namespace std;

#define ll long long
#define ld long double
#define pii pair<int, int>
#define pll pair<ll, ll>
#define mkp make_pair
#define pb push_back
#define pf push_front
#define popb pop_back
#define popf pop_front
#define ff first
#define ss second
#define endl "\\n"
#define MOD 1000000007
#define MOD1 998244353
#define inf 1e18

ll GCD(ll x, ll y) {
  if (y == 0)
    return x;
  return GCD(y, x % y);
}
ll LCM(ll x, ll y) { return (x * y) / (GCD(x, y)); }
ll LOGK(ll x, ll k) {
  if (x >= k)
    return 1 + LOGK(x / k, k);
  return 0;
}
ll MPOW(ll a, ll b, ll m) {
  if (b == 0)
    return 1;
  ll x = MPOW(a, b / 2, m);
  x = (x * x) % m;
  if (b % 2 == 1)
    x = (x * a) % m;
  return x;
}
ll MINV(ll a, ll m) { return MPOW(a, m - 2, m); }

class pnc {
  ll FACT_MAX, MODU;
  vector<ll> fact;

public:
  pnc(ll n, ll m) {
    FACT_MAX = n;
    fact.resize(FACT_MAX);
    MODU = m;
    MFACT_INIT(MODU);
  }
  void MFACT_INIT(ll m) {
    fact[0] = 1;
    for (ll i = 1; i < FACT_MAX; ++i)
      fact[i] = (i * fact[i - 1]) % MODU;
  }
  ll MFACT(ll n) { return fact[n]; }
  ll PERM(ll n, ll r) { return (fact[n] * ::MINV(fact[n - r], MODU)) % MODU; }
  ll COMB(ll n, ll r) { return (PERM(n, r) * ::MINV(fact[r], MODU)) % MODU; }
};

const ll N = 10000005;

ll dp[N] = {0};

int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);

  ll test = 1;
  // cin>>test;
  while (test--) {
    for (ll i = 1; i < N; i++) {
      for (ll j = i; j < N; j += i)
        dp[j]++;
    }

    ll ans = 0;

    ll n;
    cin >> n;

    for (ll i = 1; i <= n; i++)
      ans += (i * dp[i]);

    cout << ans;
  }
}

Error: TLE

Fixed submission:

#include <bits/stdc++.h>

using namespace std;

#define ll long long
#define ld long double
#define pii pair<int, int>
#define pll pair<ll, ll>
#define mkp make_pair
#define pb push_back
#define pf push_front
#define popb pop_back
#define popf pop_front
#define ff first
#define ss second
#define endl "\\n"
#define MOD 1000000007
#define MOD1 998244353
#define inf 1e18

ll GCD(ll x, ll y) {
  if (y == 0)
    return x;
  return GCD(y, x % y);
}
ll LCM(ll x, ll y) { return (x * y) / (GCD(x, y)); }
ll LOGK(ll x, ll k) {
  if (x >= k)
    return 1 + LOGK(x / k, k);
  return 0;
}
ll MPOW(ll a, ll b, ll m) {
  if (b == 0)
    return 1;
  ll x = MPOW(a, b / 2, m);
  x = (x * x) % m;
  if (b % 2 == 1)
    x = (x * a) % m;
  return x;
}
ll MINV(ll a, ll m) { return MPOW(a, m - 2, m); }

class pnc {
  ll FACT_MAX, MODU;
  vector<ll> fact;

public:
  pnc(ll n, ll m) {
    FACT_MAX = n;
    fact.resize(FACT_MAX);
    MODU = m;
    MFACT_INIT(MODU);
  }
  void MFACT_INIT(ll m) {
    fact[0] = 1;
    for (ll i = 1; i < FACT_MAX; ++i)
      fact[i] = (i * fact[i - 1]) % MODU;
  }
  ll MFACT(ll n) { return fact[n]; }
  ll PERM(ll n, ll r) { return (fact[n] * ::MINV(fact[n - r], MODU)) % MODU; }
  ll COMB(ll n, ll r) { return (PERM(n, r) * ::MINV(fact[r], MODU)) % MODU; }
};

const ll N = 10000005;

bool visited[N] = {false};
vector<ll> prime[N];

int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);

  ll test = 1;
  // cin>>test;
  while (test--) {
    for (ll i = 2; i < N; i++) {
      if (!visited[i]) {
        // cout<<i<<' ';
        for (ll j = i; j < N; j += i) {
          prime[j].pb(i);
          visited[j] = true;
        }
      }
    }
    // cout<<endl;

    ll ans = 1;

    ll n;
    cin >> n;

    // for(ll i=2;i<=n;i++)
    // {
    //     ll no=1;
    //     ll num=i;
    //     for(auto j:prime[i])
    //     {
    //         ll t=0;
    //         while(num%j==0)
    //         {
    //             t++;
    //             num/=j;
    //         }

    //         no*=(t+1);
    //     }

    //     ans+=(no*i);
    // }

    cout << ans;
  }
}