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  1. #include <iostream>
  2. #include <stack>
  3.  
  4. typedef std::stack<int> stack_type;
  5.  
  6. stack_type get_values(std::istream&);
  7. int evaluate(stack_type&, std::istream&);
  8.  
  9. int main()
  10. {
  11.     std::cout << "Enter your postfix expression:\n> ";
  12.     stack_type s = get_values(std::cin);    // leaves the operation tokens in the input stream.
  13.     std::cout << evaluate(s, std::cin) << '\n';
  14. }
  15.  
  16. int evaluate(stack_type& s, std::istream& op_stream)
  17. {
  18.     while (s.size() > 1)
  19.     {
  20.         int a = s.top();
  21.         s.pop();
  22.  
  23.         int b = s.top();
  24.         s.pop();
  25.  
  26.         char op;
  27.         op_stream >> op;
  28.  
  29.         int result;
  30.         switch (op)
  31.         {
  32.         case '+': result = a + b; break;
  33.         }
  34.  
  35.         s.push(result);
  36.     }
  37.  
  38.     return s.top();
  39. }
  40.  
  41. stack_type get_values(std::istream& val_stream)
  42. {
  43.     stack_type stack;
  44.  
  45.     for (unsigned i=0; i<3; ++i)
  46.     {
  47.     	int value ;
  48.     	val_stream >> value ;
  49.     	stack.push(value) ;
  50.     }
  51.  
  52.     return stack;
  53. }
  54.  
Success #stdin #stdout 0s 3436KB
comments (?)
stdin 
1 2 3 + +
stdout 
Enter your postfix expression:
> 6
https://ideone.com/vARynI
language:
C++14 (gcc 8.3)
created:
10 years ago
visibility:
public

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