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  1. /*
  2.  * Language: Standard C++23 [-std=c++23]
  3.  * Author: Zang Vũ aka zvwgvx
  4.  * Github & Discord & Facebook: @zvwgvx
  5.  */
  6.  
  7. #pragma GCC optimize("fast-math,O3")
  8. #pragma GCC optimize("no-stack-protector") 
  9. #pragma GCC optimize("unroll-loops")
  10. // #pragma GCC optimize("Ofast")
  11. // #pragma GCC target("tune=native")
  12. // #pragma GCC target("avx,avx2,fma")
  13.  
  14. #include <bits/stdc++.h>
  15.  
  16. using namespace std;
  17.  
  18. #define ENV defined(LOCAL)
  19. #define el cout << '\n'
  20. #define ll long long
  21. #define ull unsigned ll
  22. #define vi vector <int>
  23. #define vl vector <ll>
  24. #define vvi vector <vector <int>>
  25. #define vvl vector <vector <ll>>
  26. #define mts multiset
  27. #define mtm multimap
  28. #define ump unordered_map
  29. #define ust unordered_set
  30. #define umts unordered_multiset
  31. #define umtm unordered_multimap
  32. #define priq priority_queue
  33.  
  34. template <typename T>
  35. T fgcd(T a, T b) {
  36.     if (!a || !b) return a | b;
  37.     unsigned shift = __builtin_ctzll(a | b);
  38.     a >>= __builtin_ctzll(a);
  39.     while (b) {
  40.         b >>= __builtin_ctzll(b);
  41.         if (a > b) swap(a, b);
  42.         b -= a;
  43.     }
  44.     return a << shift;
  45. }
  46. template <typename T> T lcm(T a, T b) { return a * (b / fgcd(a, b)); }
  47. template <typename T> void maximize(T& a, T b) { if (a < b) a = b; }
  48. template <typename T> void minimize(T& a, T b) { if (a > b) a = b; }
  49. template <typename T> double lg(T a, T b) { return log(b) / log(a); }
  50. template <typename T> bool equal(T a, T b) { return abs(a - b) <= 1e-9; }
  51.  
  52. const int MOD = 1e9 + 7;
  53. const int INF = 1e9;
  54. const int LIMIT = 1e6 + 5;
  55.  
  56. #if ENV
  57. void open(const string& file) {
  58.     freopen((file + ".inp").c_str(), "r", stdin);
  59.     freopen((file + ".out").c_str(), "w", stdout);
  60. }
  61. auto start = clock();
  62. void time() { cout << "\n\n[rt] " << 1.0 * (clock() - start) / CLOCKS_PER_SEC; }
  63. #endif
  64.  
  65. signed main() { 
  66.     cin.tie(nullptr), cout.tie(nullptr)
  67.     -> ios_base::sync_with_stdio(false);
  68.  
  69.     #if ENV 
  70.         open("main");
  71.         srand(time(nullptr));
  72.     #endif
  73.  
  74.     vi divs(LIMIT);
  75.     for (int i = 1; i * i <= LIMIT; ++i) {
  76.         // đánh dấu các con j nhận i là ước
  77.         for (int j = i * i; j <= LIMIT; j += i) {
  78.             if (j == i * i) ++divs[j]; // +1 đơn vị vào (j nhận i là ước và j = i * i)
  79.             else divs[j] += 2; // +2 đơn vị vào vì j nhận i và j / i là ước)
  80.         }
  81.     }
  82.  
  83.  
  84.     #if ENV 
  85.         time();
  86.     #endif
  87.  
  88.     return 0;   
  89. }
Success #stdin #stdout 0.02s 6844KB
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https://ideone.com/2tQxVX
language:
C++14 (clang 8.0)
created:
38 days ago
visibility:
public

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