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  1. /*
  2. " وَكَانَ فَضْلُ اللَّهِ عَلَيْكَ عَظِيمًا "
  3.  
  4. ╔░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░╗
  5. ║                                                                                           ║
  6. ║   ███╗   ███╗ ██████╗ ██╗  ██╗  █████╗  ███╗   ███╗ ███████╗ ██████╗                      ║
  7. ║   ████╗ ████║██╔═══██╗██║  ██║ ██╔══██╗ ████╗ ████║ ██╔════╝ ██╔══██╗                     ║
  8. ║   ██╔████╔██║██║   ██║███████║ ███████║ ██╔████╔██║ █████╗   ██║  ██║                     ║
  9. ║   ██║╚██╔╝██║██║   ██║██╔══██║ ██╔══██║ ██║╚██╔╝██║ ██╔══╝   ██║  ██║                     ║
  10. ║   ██║ ╚═╝ ██║╚██████╔╝██║  ██║ ██║  ██║ ██║ ╚═╝ ██║ ███████╗ ██████╔╝                     ║
  11. ║   ╚═╝     ╚═╝ ╚═════╝ ╚═╝  ╚═╝ ╚═╝  ╚═╝ ╚═╝     ╚═╝ ╚══════╝ ╚═════╝                      ║
  12. ║                                                                                           ║
  13. ║      ██╗  ██╗  ██████╗  ███████╗ ███████╗  █████╗  ███╗   ███╗                            ║
  14. ║      ██║  ██║ ██╔═══██╗ ██╔════╝ ██╔════╝ ██╔══██╗ ████╗ ████║                            ║
  15. ║      ███████║ ██║   ██║ ███████╗ ███████╗ ███████║ ██╔████╔██║                            ║
  16. ║      ██╔══██║ ██║   ██║ ╚════██║ ╚════██║ ██╔══██║ ██║╚██╔╝██║                            ║
  17. ║      ██║  ██║ ╚██████╔╝ ███████║ ███████║ ██║  ██║ ██║ ╚═╝ ██║                            ║
  18. ║      ╚═╝  ╚═╝  ╚═════╝  ╚══════╝  ╚══════╝╚═╝  ╚═╝ ╚═╝     ╚═╝                            ║
  19. ║                                                                                           ║
  20. ╚░░░░░░░░░░░░░░░░░░░░░░░ MOHAMED HOSSAM | SOFTWARE ENGINEER ░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░╝
  21. */
  22.  
  23. #include"bits/stdc++.h"
  24. using namespace std;
  25. #define el '\n'
  26. #define ll long long
  27. #define int long long
  28. #define yes cout << "YES\n"
  29. #define no cout << "NO\n"
  30. #define all(x) (x).begin(), (x).end()
  31. #define rall(x) x.rbegin(), x.rend()
  32. #define sz(x) ((int)(x).size())
  33.  
  34. template<class T, class U>
  35. T GCD(T a, U b) { return (!b ? a : GCD(b, a % b)); }
  36.  
  37. template<class T, class U>
  38. T LCM(T a, U b) { return ((a / GCD(a, b)) * b); }
  39.  
  40. template<class Ta, class Tb>
  41. bool chmax(Ta &a, Tb b) {
  42.     if (a >= b) return false;
  43.     a = b;
  44.     return true;
  45. }
  46.  
  47. template<class Ta, class Tb>
  48. bool chmin(Ta &a, Tb b) {
  49.     if (a <= b) return false;
  50.     a = b;
  51.     return true;
  52. }
  53.  
  54. constexpr ll MAX = 300000, MOD = 998244353, MAXN = 2e5 + 10, inf = 1e18;
  55. using vi = vector<int>;
  56. int dx[] = {-1, 1, 0, 0};
  57. int dy[] = {0, 0, -1, 1};
  58. inline void free_palestine() {
  59.     ios_base::sync_with_stdio(false);
  60.     cin.tie(NULL);
  61.     cout.tie(NULL);
  62.  
  63. #ifndef ONLINE_JUDGE
  64.     freopen("inputs.txt", "r", stdin);
  65.     freopen("output.txt", "w", stdout);
  66. #endif
  67. }
  68.  
  69. template<typename T>
  70. istream &operator>>(istream &in, vector<T> &v) {
  71.     for (auto &x: v) in >> x;
  72.     return in;
  73. }
  74.  
  75. template<typename T>
  76. ostream &operator<<(ostream &out, const vector<T> &v) {
  77.     for (const auto &x: v) out << x << ' ';
  78.     return out;
  79. }
  80.  
  81. void solve(int tc) {
  82.     int n;cin>>n;
  83.     vi a(n), pref(n+1), pref_sq(n + 1);
  84.     for (int i=0;i<n;i++) {
  85.         cin>>a[i];
  86.         pref[i+1] = pref[i]+a[i];
  87.         pref_sq[i+1] = pref_sq[i] + a[i] * a[i];
  88.     }
  89.  
  90.     int ans = 0;
  91.     for (int i=0;i<n;i++) {
  92.         int cnt_a = n-1-i,
  93.         sum1 = pref[n] - pref[i + 1],
  94.         sum2 = pref_sq[n] - pref_sq[i + 1];
  95.  
  96.         ans += (a[i] * a[i] *cnt_a) + (2 * a[i] * sum1)+sum2;
  97.     }
  98.  
  99.     cout<<ans<<el;
  100. }
  101.  
  102. int32_t main() {
  103.     free_palestine();
  104.     // freopen("collectingofficer.in", "r", stdin);// freopen("palindrome.out", "w", stdout);
  105.     int tc = 1;
  106.  
  107.    // cin >> tc;
  108.     for (int i = 1; i <= tc; ++i) {
  109.         solve(i);
  110.     }
  111.  
  112.     /*
  113.     ⢸⠉⠉⠉⠉⠉⠉⠉⠉⠉⠉⠉⠉⠉⡷⠀⠀
  114.     ⢸⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀ ⠀⠢⣀⠀⠀
  115.     ⢸⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⡇ Did you get accepted, son?
  116.     ⢸⠀⠀⠀⠀ ⠖⠒⠒⠒⢤⠀⠀⠀⠀⠀⡇⠀⠀
  117.     ⢸⠀⠀⣀⢤⣼⣀⡠⠤⠤⠼⠤⡄⠀⠀⡇⠀
  118.     ⢸⠀⠀⠑⡤⠤⡒⠒⠒⡊⠙⡏⠀⢀⠀⡇⠀
  119.     ⢸⠀⠀⠀⠇⠀⣀⣀⣀⣀⢀⠧⠟⠁ ⡇
  120.     ⢸⠀⠀⠀⠸⣀⠀⠀⠈⢉⠟⠓⠀⠀⠀⢀⡇⠀⠀
  121.     ⢸⠀⠀⠀⠀⠈⢱⡖⠋⠁⠀⠀⠀⠀⠀⡇⠀⡇
  122.     ⢸⠀⠀⠀⠀⣠⢺⠧⢄⣀⠀⠀⣀⣀⠀⡇⠀⡇
  123.     ⢸⠀⠀⠀⣠⠃⢸⠀⠀⠈⠉⡽⠿⠯⡆⡇
  124.     ⢸⠀⠀⣰⠁⠀⢸⠀⠀⠀⠀⠉⠉⠉⠀⡇⠀⡇
  125.     ⢸⠀⠀⠣⠀⠀⢸⢄⠀⠀⠀⠀⠀⠀⠀⡇⠀⡇⠀
  126.     ⢸⠀⠀⠀⠀⠀⢸⠀⢇⠀⠀⠀⠀⠀⠀⡇⠀⡇
  127.     ⠉⠉⠉⠉⠉⠉⠉⠉⠉⠉⠉⠉⠉⠉⠉⠉⠉⠉
  128.     */
  129. }
  130.  
Success #stdin #stdout 0.01s 5312KB
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https://ideone.com/slo7SO
language:
C++ (gcc 8.3)
created:
22 hours ago
visibility:
public

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