fork download
copy 
  1. #include <iostream>
  2. #include <sstream>
  3. #include <vector>
  4. #include <utility>
  5.  
  6. std::istream& Char( std::istream& is,
  7.     			    char ch,
  8. 					bool skipws = true )
  9. {
  10. 	if( skipws )
  11. 		is >> std::ws;
  12. 	if( is.get() != ch )
  13. 		is.setstate( std::ios_base::failbit );
  14. 	return is;
  15. }
  16.  
  17. int main()
  18. {
  19. 	std::istringstream stream("2x^4-5x^3+3.5x^2+2x-5");
  20.  
  21. 	using Real = double;
  22.  
  23. 	std::vector<std::pair<Real, Real>> values;
  24.  
  25. 	for(;;)
  26. 	{
  27. 		Real a, b;
  28.  
  29. 		if( !(stream >> std::ws >> a) )
  30. 			break;
  31.  
  32. 		bool succeeded_x = false;
  33. 		if( !Char(stream, 'x')
  34. 		 || (succeeded_x = true, !Char(stream, '^')) )
  35. 		{
  36. 			stream.clear();
  37. 			stream.unget();
  38. 			b = succeeded_x;
  39. 		}
  40.  
  41. 		else if( !(stream >> std::ws >> b) )
  42. 			break;
  43.  
  44. 		values.emplace_back(a, b);
  45.  
  46. 		if( stream.peek() != '+' 
  47. 		 && stream.peek() != '-' )
  48. 			break;
  49. 	}
  50.  
  51. 	for( auto const& p : values )
  52. 		std::cout << p.first << " * x^" << p.second << '\n';
  53. }
Success #stdin #stdout 0s 2988KB
comments (?)
stdin
copy 
Standard input is empty
stdout
copy 
2 * x^4
-5 * x^3
3.5 * x^2
2 * x^1
-5 * x^0
https://ideone.com/f84SDe
language:
C++14 (gcc 8.3)
created:
10 years ago
visibility:
public

Share or Embed source code

Discover > Sphere Engine API

The brand new service which powers Ideone!

Discover > IDE Widget

Widget for compiling and running the source code in a web browser!