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  1. #include <iostream>
  2. #include <type_traits>
  3. #include <limits>
  4. using namespace std;
  5.  
  6.     template <class integral_type>
  7.     typename std::enable_if<std::is_integral<integral_type>::value, integral_type>::type NoOverflowMult(const integral_type a, const integral_type b)
  8.     {
  9.     	if (!a || !b)
  10.     		return integral_type();
  11.  
  12.     	integral_type bound = ((a < 0) != (b < 0) ? std::numeric_limits<integral_type>::min() : std::numeric_limits<integral_type>::max());
  13.  
  14.     	if (std::abs(bound / a) < std::abs(b))
  15.     		return bound;
  16.     	return a*b;
  17.     }
  18.  
  19. int main() 
  20. {
  21. 	std::cout << "int" << std::endl;
  22. 	int ai = 2147483600;
  23. 	int bi = -1234;
  24. 	std::cout << ai << " * " << bi << " = " << NoOverflowMult(ai,bi) << std::endl;
  25. 	ai = std::numeric_limits<int>::min ();
  26. 	bi = 2;
  27. 	std::cout << ai << " * " << bi << " = " << NoOverflowMult(ai,bi) << std::endl;
  28.  
  29. 	std::cout << "unsigned short" << std::endl;
  30.  
  31. 	unsigned short aus = 65000;
  32. 	unsigned short bus = 2;
  33. 	std::cout << aus << " * " << bus << " = " << NoOverflowMult(aus,bus) << std::endl;
  34. 	aus = std::numeric_limits<unsigned short>::max();
  35. 	bus = std::numeric_limits<unsigned short>::min();
  36. 	std::cout << aus << " * " << bus << " = " << NoOverflowMult(aus,bus) << std::endl;
  37. 	return 0;
  38. }
Success #stdin #stdout 0s 3340KB
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stdin
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Standard input is empty
stdout
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int
2147483600 * -1234 = -2147483648
-2147483648 * 2 = -2147483648
unsigned short
65000 * 2 = 65535
65535 * 0 = 0
https://ideone.com/emMyaA
language:
C++14 (gcc 8.3)
created:
9 years ago
visibility:
public

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