Reverse Polish Calculator - C++ STL

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Description

Reverse Polish Calculator

Demo Code

#include <iostream>
#include <cstring>
#include <stack>
using namespace std;
#define MAX_CHARS 100//from   w  w  w . j av a2 s  .c o m
int main()
{
   char input_str[MAX_CHARS], *p;
   stack<double>  num_stack;
   int c;
   double a, b, n;
   cout << "Enter RPN string: ";
   cin.getline(input_str, MAX_CHARS);
   p = strtok(input_str, " ");
   while (p) {
      c = p[0];
      if(c == '+' || c == '*' || c == '/' || c == '-'){
         if (num_stack.size() < 2) {
            cout << "Error: too many ops."<< endl;
            return -1;
         }
         b = num_stack.top(); num_stack.pop();
         a = num_stack.top(); num_stack.pop();
         switch (c) {
            case '+': n = a + b; break;
            case '*': n = a * b; break;
            case '/': n = a / b; break;
            case '-': n = a - b; break;
         }
         num_stack.push(n);
      } else {
         num_stack.push(atof(p));
      }
      p = strtok(nullptr, " ");
   }
   cout <<"The answer is: " << num_stack.top()<< endl;
   return 0;
}

Result


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