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  1. #include<bits/stdc++.h> 
  2.  
  3. using namespace std;
  4.  
  5. using ldbl = long double;
  6. using ll   =   long long;
  7.  
  8. const ldbl delta = 1e-9; const int N = 10; ll m[N], n[N], t[N]; 
  9.  
  10. namespace timer
  11. {
  12.     typedef chrono::high_resolution_clock     Clock_t;
  13.     typedef chrono::time_point<Clock_t>        Time_t;
  14.     typedef chrono::microseconds          Time_scale_t;
  15.  
  16.     static Time_t present;
  17.  
  18.     inline void reset()
  19.     {
  20.         present = Clock_t::now();
  21.     }
  22.  
  23.     inline ll elapsed_time()
  24.     {
  25.         auto past = present; reset();
  26.  
  27.         return chrono::duration_cast<Time_scale_t>(present-past).count();
  28.     }
  29. }
  30.  
  31. int main()
  32. {
  33.     ios_base::sync_with_stdio(false), cin.tie(nullptr), cout.tie(nullptr); 
  34.  
  35.     n[0] = 1, timer::reset();
  36.  
  37.     for(int j = 0; j < N; j++, n[j] = n[j-1]*10)
  38.     {
  39.         for(ldbl i_max = 1/ldbl(n[j]), i = 0; i <= i_max; i += delta)
  40.             m[j]++;
  41.  
  42.         t[j] = timer::elapsed_time();
  43.     }
  44.  
  45.     for(int j = 0; j < N; j++)
  46.         cout << j << ": n = " << n[j] << ", ",
  47.         cout << m[j] << " iteration(s), total loop execution-time = " << t[j] << " usec" << endl;
  48. }
Success #stdin #stdout 1.15s 15240KB
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0: n = 1, 1000000000 iteration(s), total loop execution-time = 1039169 usec
1: n = 10, 100000000 iteration(s), total loop execution-time = 104531 usec
2: n = 100, 10000001 iteration(s), total loop execution-time = 10602 usec
3: n = 1000, 1000000 iteration(s), total loop execution-time = 1053 usec
4: n = 10000, 100000 iteration(s), total loop execution-time = 107 usec
5: n = 100000, 10001 iteration(s), total loop execution-time = 10 usec
6: n = 1000000, 1000 iteration(s), total loop execution-time = 1 usec
7: n = 10000000, 100 iteration(s), total loop execution-time = 0 usec
8: n = 100000000, 10 iteration(s), total loop execution-time = 0 usec
9: n = 1000000000, 1 iteration(s), total loop execution-time = 0 usec
https://ideone.com/92kGIv
O(m) linear-time complexity
language:
C++14 (gcc 8.3)
created:
5 years ago
visibility:
public

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