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  1. #include <iostream>
  2. #include <cstring>
  3.  
  4. using namespace std;
  5.  
  6. template<class T>
  7. class Stack
  8. {
  9. private:
  10.     T *s;
  11.     int N;
  12.  
  13. public:
  14.     Stack(int maxn)
  15.     {
  16.         s = new T[maxn];
  17.         N = 0;
  18.     }
  19.     int empty()const
  20.     {
  21.         return N == 0;
  22.     }
  23.     void push(T k)
  24.     {
  25.         s[N++] = k;
  26.     }
  27.     T pop()
  28.     {
  29.         return s[--N];
  30.     }
  31. };
  32.  
  33. int main()
  34. {
  35.     //postfix evaluation
  36.     const char *a = "3 4 5*+";
  37.     int N = strlen(a);
  38.  
  39.     Stack<int>save(N);
  40.  
  41.     for (int i = 0; i < N; i++)
  42.     {
  43.         if (a[i]=='+')
  44.             save.push(save.pop() + save.pop());
  45.  
  46.         if (a[i]=='*')
  47.             save.push(save.pop() * save.pop());
  48.  
  49.         if (a[i] >= '0' && a[i] <= '9')
  50.         {
  51.             save.push(0);
  52.             while (a[i] >= '0' && a[i] <= '9')
  53.                 save.push(10 * save.pop() + a[i++] - '0');
  54.             i--;
  55.         }
  56.     }
  57.  
  58.     cout << save.pop() << "  " << endl;
  59.  
  60.     return 0;
  61. }
  62.  
Success #stdin #stdout 0.02s 2856KB
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https://ideone.com/5osxt
language:
C++ (gcc 8.3)
created:
13 years ago
visibility:
public

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