fork download 
  1. #include <iostream>
  2. #include <stack> // don't have time to implement a stack by myself
  3. using namespace std;
  4.  
  5. // function to check precedence
  6. int pre(char op);
  7.  
  8. int main()
  9. {
  10.     string infix;
  11.     cout << "Expression: ";
  12.     cin >> infix;
  13.  
  14.     stack<char> st;
  15.     string postfix = "";
  16.     for (int i = 0; i < infix.length(); i++)
  17.     {
  18.         char c = infix[i];
  19.         if (c >= '0' && c <= '9') // To make sure we are adding any number we meet
  20.             postfix += c;
  21.  
  22.         else if (c == '(') // open prenthesess are added to our cup
  23.             st.push(c);
  24.  
  25.         else if (c == ')')
  26.         {
  27.             // making sure we are poping from not empty stack
  28.             while (!st.empty() && st.top() != '(')
  29.             {
  30.                 postfix += st.top();
  31.                 st.pop();
  32.             }
  33.             st.pop(); // to remove one '(', aka remove one open prentheesss
  34.         }
  35.         else if (c == '+' || c == '-' || c == '*' || c == '/' || c == '^')
  36.         {
  37.             while (!st.empty() && pre(st.top()) >= pre(c))
  38.             {
  39.                 postfix += st.top();
  40.                 st.pop();
  41.             }
  42.             st.push(c);
  43.         }
  44.     }
  45.     while (!st.empty())
  46.     {
  47.         postfix += st.top();
  48.         st.pop();
  49.     }
  50.  
  51.     cout << "After Converting To Postfix: " << postfix;
  52.  
  53.     return 0;
  54. }
  55.  
  56. // What comes before the other ..uuuh
  57. int pre(char op)
  58. {
  59.     if (op == '^')
  60.         return 3;
  61.     if (op == '*' || op == '/')
  62.         return 2;
  63.     if (op == '+' || op == '-')
  64.         return 1;
  65.     return 0;
  66. }
Success #stdin #stdout 0s 5280KB
comments (?)
stdin 
Standard input is empty
stdout 
Expression: After Converting To Postfix:
https://ideone.com/KiB4f5
language:
C++ (gcc 8.3)
created:
1 day 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!