Problem p02572 (C++) — buggy submission, verdict: Time Limit Exceeded

/*
    written by Pankaj Kumar.
    country:-INDIA
*/
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef set<pair<int, int>> spi;
typedef set<pair<ll, ll>> spl;
typedef vector<pair<int, int>> vpi;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef vector<bool> vb;
typedef vector<char> vc;
typedef vector<pair<ll, ll>> vpl;
typedef vector<string> vs;
typedef map<ll, ll> ml;
typedef set<string> ss;
typedef set<char> sc;
typedef set<int> si;
typedef set<ll> sl;
#define pan                                                                    \\
  cin.tie(0);                                                                  \\
  cout.tie(0);                                                                 \\
  ios_base::sync_with_stdio(0);
// define values.
#define mod 1000000007
#define phi 1.618
/* Bit-Stuff */
#define get_set_bits(a) (__builtin_popcount(a))
#define get_set_bitsll(a) (__builtin_popcountll(a))
#define get_trail_zero(a) (__builtin_ctz(a))
#define get_lead_zero(a) (__builtin_clz(a))
#define get_parity(a) (__builtin_parity(a))
/*  Abbrevations  */
#define ff first
#define ss second
#define mp make_pair
#define line cout << endl;
#define pb push_back
#define Endl "\\n"
// loops
#define loop(i, start, end) for (ll i = ll(start); i < ll(end); i++)
#define loop0(num) for (ll i = 0; i < ll(num); i++)
#define forin(arr, n)                                                          \\
  for (ll i = 0; i < n; i++)                                                   \\
    cin >> arr[i];
// Some print
#define no cout << "NO" << endl;
#define yes cout << "YES" << endl;
#define cc                                                                     \\
  ll test;                                                                     \\
  cin >> test;                                                                 \\
  while (test--)
// sort
#define all(V) (V).begin(), (V).end()
#define srt(V) sort(all(V))
#define srtGreat(V) sort(all(V), greater<ll>())
// function

ll power(ll x, ll y) {
  ll res = 1;
  while (y > 0) {
    if (y % 2 == 1)
      res *= x;
    y /= 2;
    x *= x;
  }
  return res;
}
/* ascii value
A=65,Z=90,a=97,z=122
*/
/*  -----------------------------------------------------------------------------------*/
ll solve() {
  ll n;
  cin >> n;
  ll ans = 0, sum = 0;
  ll temp = 0;
  for (ll i = 0; i < n; i++) {
    cin >> temp;
    ans += sum * temp;
    sum += temp;
    ans %= mod;
    sum %= mod;
  }
  cout << ans << endl;
  return 0;
}

int main() {
  // freopen("input.txt"a, "r", stdin);
  //  cc
  //  {
  solve();
  // }
}


Error: TLE

Fixed submission:

/*
    written by Pankaj Kumar.
    country:-INDIA
*/
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef set<pair<int, int>> spi;
typedef set<pair<ll, ll>> spl;
typedef vector<pair<int, int>> vpi;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef vector<bool> vb;
typedef vector<char> vc;
typedef vector<pair<ll, ll>> vpl;
typedef vector<string> vs;
typedef map<ll, ll> ml;
typedef set<string> ss;
typedef set<char> sc;
typedef set<int> si;
typedef set<ll> sl;
#define pan                                                                    \\
  cin.tie(0);                                                                  \\
  cout.tie(0);                                                                 \\
  ios_base::sync_with_stdio(0);
// define values.
#define mod 1000000007
#define phi 1.618
/* Bit-Stuff */
#define get_set_bits(a) (__builtin_popcount(a))
#define get_set_bitsll(a) (__builtin_popcountll(a))
#define get_trail_zero(a) (__builtin_ctz(a))
#define get_lead_zero(a) (__builtin_clz(a))
#define get_parity(a) (__builtin_parity(a))
/*  Abbrevations  */
#define ff first
#define ss second
#define mp make_pair
#define line cout << endl;
#define pb push_back
#define Endl "\\n"
// loops
#define loop(i, start, end) for (ll i = ll(start); i < ll(end); i++)
#define loop0(num) for (ll i = 0; i < ll(num); i++)
#define forin(arr, n)                                                          \\
  for (ll i = 0; i < n; i++)                                                   \\
    cin >> arr[i];
// Some print
#define no cout << "NO" << endl;
#define yes cout << "YES" << endl;
#define cc                                                                     \\
  ll test;                                                                     \\
  cin >> test;                                                                 \\
  while (test--)
// sort
#define all(V) (V).begin(), (V).end()
#define srt(V) sort(all(V))
#define srtGreat(V) sort(all(V), greater<ll>())
// function

ll power(ll x, ll y) {
  ll res = 1;
  while (y > 0) {
    if (y % 2 == 1)
      res *= x;
    y /= 2;
    x *= x;
  }
  return res;
}
/* ascii value
A=65,Z=90,a=97,z=122
*/
/*  -----------------------------------------------------------------------------------*/
ll solve() {
  ll n;
  cin >> n;
  vl v(n);
  forin(v, n);
  ll ans = 0;
  for (ll i = 0; i < n; i++) {
    ll sum = 0;
    for (ll j = i + 1; j < n; j++)
      sum += v[j];
    sum = sum % 1000000007;
    ans += (sum * v[i]);
    ans = ans % 1000000007;
  }
  cout << ans % 1000000007 << endl;
  return 0;
}

int main() {
  // freopen("input.txt"a, "r", stdin);
  //  cc
  //  {
  solve();
  // }
}