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  1. #include <iostream>
  2. #include <vector>
  3. #include <climits>
  4. #include <cstdlib>
  5. #include <ctime>
  6. #include <random>
  7. #include <iomanip>
  8. using namespace std;
  9.  
  10. unsigned int myConcat(unsigned int& a, unsigned int& b) {
  11. 	switch( (b >= 10000000) ? 7 : 
  12. 			(b >= 1000000) ? 6 : 
  13. 			(b >= 100000) ? 5 : 
  14. 			(b >= 10000) ? 4 : 
  15. 			(b >= 1000) ? 3 : 
  16. 			(b >= 100) ? 2 : 
  17. 			(b >= 10) ? 1 : 0 ) {
  18. 		case 1: return a*100+b; break;
  19.     	case 2: return a*1000+b; break;
  20.     	case 3: return a*10000+b; break;
  21.     	case 4: return a*100000+b; break;
  22.     	case 5: return a*1000000+b; break;
  23.     	case 6: return a*10000000+b; break;
  24.     	case 7: return a*100000000+b; break;
  25.     	default: return a*10+b; break;
  26.     	// I don't really know what to do here
  27.     	//case 8: return a*1000*1000*1000+b; break;
  28.     	//case 9: return a*10*1000*1000*1000+b; break;
  29. 	}
  30. }
  31.  
  32. unsigned int uintcat (unsigned int& ms, unsigned int& ls) {
  33. 	unsigned int mult;
  34. 	for(mult=10; mult <= ls; mult *= 10) {}
  35. 	return ms * mult + ls;
  36. }
  37.  
  38. int main() {
  39. 	default_random_engine generator;
  40.   	uniform_int_distribution<unsigned int> distrA(0,9),distrB(0,100*1000*1000);
  41.   	int i;
  42.  
  43.   	int testCnt = 10*1000*1000;
  44.   	time_t start_time;
  45. 	cout << setprecision(3) << fixed;
  46.  
  47.   	vector<unsigned int> a(testCnt), b(testCnt);
  48.   	for(i = 0; i < testCnt; i++)
  49. 		a[i] = distrA(generator), b[i] = distrB(generator);
  50.  
  51. 	start_time = clock();
  52. 	for(i = 0; i < testCnt; ++i)
  53. 		myConcat(a[i], b[i]);
  54. 	cout << (clock()-start_time)/double(CLOCKS_PER_SEC) << "\n";
  55.  
  56. 	// use separate vectors to overcome memory hashing, but data is the same
  57. 	vector<unsigned int> c(a.begin(), a.end()), d(b.begin(), b.end());
  58. 	start_time = clock();
  59. 	for(i = 0; i < testCnt; ++i)
  60. 		uintcat(c[i], d[i]);
  61. 	cout << (clock()-start_time)/double(CLOCKS_PER_SEC) << "\n";
  62.  
  63. 	return 0;
  64. }
Success #stdin #stdout 1.38s 3344KB
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https://ideone.com/Cl5oix
language:
C++14 (gcc 8.3)
created:
11 years ago
visibility:
public

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