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  1. #include <list>
  2. #include <vector>
  3. #include <map>
  4. #include <functional>
  5. #include <iostream>
  6. #include <algorithm>
  7. #include <initializer_list>
  8.  
  9. class program {
  10. 	typedef std::list <int> args_t;
  11. 	typedef std::function<int(int,int)> op_t;
  12. 	typedef std::vector <op_t> code_t;
  13.  
  14. 	args_t args;
  15. 	code_t code;
  16.  
  17. 	public:
  18.  
  19. 	void compile (const std::string& expr) {
  20. 	  static std::map <char, op_t> op_map = {
  21. 	  	{'+', std::plus<int>() }
  22. 	   ,{'-', std::minus<int>() }
  23. 	  };
  24.  
  25. 	  for (auto c: expr) {
  26. 	    isdigit(c) ? 
  27. 	    	args.push_back (c-'0') 
  28. 	      : code.push_back (op_map[c]);
  29. 	  }
  30. 	}
  31.  
  32. 	int next_arg () {
  33. 		int arg = *args.begin (); args.pop_front();
  34. 		return arg;
  35. 	}
  36.  
  37. 	int run () {
  38. 	  for (auto op: code) {
  39. 		int lhs = next_arg();
  40. 	  	int rhs = next_arg();
  41. 	    args.push_front (op (lhs, rhs));
  42. 	  }
  43. 	  return next_arg();
  44. 	}
  45. };
  46.  
  47. int main()
  48. {
  49.  
  50.   program p;
  51.   p.compile ("7+3-2+5");
  52.   int result = p.run ();
  53.   std::cout << result; // 13
  54. }
  55.  
Success #stdin #stdout 0s 3432KB
comments (?)
stdin 
Standard input is empty
stdout 
13
https://ideone.com/jcECGV
language:
C++14 (gcc 8.3)
created:
13 years ago
visibility:
public

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