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  1. #include <iostream>
  2. #include <iomanip>
  3. using namespace std;
  4.  
  5. // Let's see if this works !!!
  6. // (After all, I might have screwed up somewhere, so there's no guarantees!)
  7.  
  8. unsigned int sqrtOfLong(unsigned long x) {
  9.   // inspired by https://w...content-available-to-author-only...e.com/watch?v=haaCoVrGd6k
  10.   unsigned long leftover     = x;
  11.   unsigned long leftoverStep = 0UL;
  12.   unsigned long result       = 0UL;
  13.   unsigned long resultStep   = 0x40000000UL;
  14.   do {
  15.     leftoverStep >>= 1;    
  16.     result       >>= 1;
  17.     if ((leftoverStep + resultStep) <= leftover) {
  18.       leftoverStep += resultStep;
  19.       leftover     -= leftoverStep;
  20.       result       += resultStep;
  21.       leftoverStep += resultStep;
  22.     }
  23.     resultStep   >>= 2;
  24.   } while (resultStep);
  25.   return ((unsigned int)result);
  26. }
  27.  
  28. int main() {
  29. 	unsigned long ok = 0;
  30. 	unsigned long ng = 0;
  31.  
  32. 	for (unsigned long i = 0; i <= 0xFFFFUL; i++) {
  33. 	  unsigned long qu = i * i;
  34. 	  unsigned int  rt = sqrtOfLong(qu);  
  35.       // cout << setw(5) << i << "  " << setw(5) << qu << "  " << setw(5) << rt << "\n";
  36.       if (i == rt) {
  37.       	ok++;
  38.       }
  39.       else {
  40.       	ng++;
  41.       }
  42.       // cout << "\n";
  43.       qu += (2*i);
  44.       rt = sqrtOfLong(qu);  
  45.       // cout << setw(5) << i << "  " << setw(5) << qu << "  " << setw(5) << rt << "\n";
  46.       if (i == rt) {
  47.       	ok++;
  48.       }
  49.       else {
  50.       	ng++;
  51.       }
  52. 	}
  53. 	cout << "\n";
  54. 	cout << "OK: " << ok << "\n";
  55. 	cout << "NG: " << ng << "\n";
  56.  
  57. 	// your code goes here
  58. 	return 0;
  59. }
Success #stdin #stdout 0s 4356KB
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stdin
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Standard input is empty
stdout
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OK: 131072
NG: 0
https://ideone.com/6oqGfz
language:
C++14 (gcc 8.3)
created:
4 years ago
visibility:
public

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