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  1. #include <iostream>
  2. #include <stack>
  3. using namespace std;
  4.  
  5. int precedence(char c)
  6. {
  7.     if (c == '^')  return 3;
  8.     else if(c=='*'|| c=='/') return 2;
  9.     else if(c=='+'|| c=='-') return 1;
  10.     else return -1;
  11. }
  12.  
  13. string InfixToPostfix(string str)
  14. {
  15.     stack<char>Stack;
  16.     string result;
  17.  
  18.     // add sentinal at end of infix exp
  19.     str = str + ')';
  20.  
  21.     Stack.push('(');
  22.  
  23.     for (int i = 0; i<str.length(); i++) 
  24.     {
  25.         char ch = str[i];
  26.         if (isdigit(ch))
  27.         {
  28.             result += ch;
  29.         }
  30.         else if (ch == '(' )
  31.         {
  32.             Stack.push(ch);
  33.         }
  34.         else if(ch == ')')
  35.         {
  36.             while (Stack.top() != '(')
  37.             {
  38.                 result += Stack.top();
  39.                 Stack.pop();
  40.             }
  41.             Stack.pop(); //Pop '('
  42.         }
  43.         else
  44.         {
  45.             while(!Stack.empty()) && (precedence(ch) <= precedence(Stack.top()))
  46.             {
  47.                 result += Stack.top();
  48.                 Stack.pop();
  49.             }
  50.             Stack.push(ch);
  51.         }
  52.     }
  53.     return result;
  54. }
  55.  
  56. int main()
  57. {
  58.     string st = "(5*(6+2) - (2/4))";
  59.     cout << "postfix exp"<< InfixToPostfix(st);
  60.     return 0;
  61.  
  62. }
Success #stdin #stdout 0.02s 25692KB
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#include <iostream>
#include <stack>
using namespace std;

int precedence(char c)
{
    if (c == '^')  return 3;
    else if(c=='*'|| c=='/') return 2;
    else if(c=='+'|| c=='-') return 1;
    else return -1;
}

string InfixToPostfix(string str)
{
    stack<char>Stack;
    string result;
    
    // add sentinal at end of infix exp
    str = str + ')';
    
    Stack.push('(');

    for (int i = 0; i<str.length(); i++) 
    {
        char ch = str[i];
        if (isdigit(ch))
        {
            result += ch;
        }
        else if (ch == '(' )
        {
            Stack.push(ch);
        }
        else if(ch == ')')
        {
            while (Stack.top() != '(')
            {
                result += Stack.top();
                Stack.pop();
            }
            Stack.pop(); //Pop '('
        }
        else
        {
            while(!Stack.empty()) && (precedence(ch) <= precedence(Stack.top()))
            {
                result += Stack.top();
                Stack.pop();
            }
            Stack.push(ch);
        }
    }
    return result;
}

int main()
{
    string st = "(5*(6+2) - (2/4))";
    cout << "postfix exp"<< InfixToPostfix(st);
    return 0;

}
https://ideone.com/Wz6FIJ
language:
PHP (php 7.3.5)
created:
18 hours ago
visibility:
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