infix to postfix by Mam

infix_postfix_mam.cpp

// This program will convert an
//infix expression to postfix expression.
//Shemul Hossain

#include <iostream>
#include <stack>
#include <string>

using namespace std;

int priority(char x)
{
    switch(x)
    {
        case '(':
        case '#':
            return 0;
        case '+':
        case '-':
            return 1;
        case '*':
        case '/':
            return 2;
    }
}

int main()
{
    //char infix[20]={'2','*','3','/','(','2','-','1',')','+','5','*','3','\0'}, postfix[20], c;
    string infix;
    char postfix[20],c;
    int i,k=0;

    stack<char>st;
    st.push('#');


    cout<< "Enter your infix expression here: "<<endl;
    cin>>infix;



    for(i=0; infix[i]!='\0'; i++)
    {
        c = infix[i];


        if(c == '(')
        {
            st.push(c);
        }
        else if (c==')')
        {
            while(st.top()!='(')
            {
                postfix[k++]=st.top();
                st.pop();
            }
            st.pop();

        }
        else if (c=='+' || c=='-' || c=='*' || c=='/' || c=='%' )
        {
            while (priority(c)<=priority(st.top()))
            {
                if(st.top()!='#')
                {
                    postfix[k++]=st.top();
                }
                st.pop();

            }

            st.push(c);
        }
        else
        {
            postfix[k++]=c;
        }

    }
    while(!st.empty())
    {
            postfix[k++]=st.top();
            st.pop();
    }
    postfix[k]='\0';

    cout<<"Converted Postfix expression:  "<<endl;
    for(int i=0; postfix[i]!='\0'; i++)
    {
        cout<<postfix[i];
    }
    cout<<endl;
}