Infix to Postfix.cpp

//{ Driver Code Starts
// C++ implementation to convert infix expression to postfix
#include <bits/stdc++.h>
using namespace std;

// } Driver Code Ends
class Solution
{
public:
    // Function to convert an infix expression to a postfix expression.
    int prec(char c)
    {
        if (c == '^')
        {
            return 3;
        }
        else if (c == '*' || c == '/')
        {
            return 2;
        }
        else if (c == '+' || c == '-')
        {
            return 1;
        }
        else
        {
            return -1;
        }
    }
    string infixToPostfix(string s)
    {
        string res;
        stack<char> st;
        for (int i = 0; i < s.length(); i++)
        {
            if ((s[i] >= 'A' and s[i] <= 'Z') or (s[i] >= 'a' and s[i] <= 'z'))
            {
                res += s[i];
            }
            else if (s[i] == '(')
            {
                st.push(s[i]);
            }
            else if (s[i] == ')')
            {
                while (!st.empty() and st.top() != '(')
                {
                    res += st.top();
                    st.pop();
                }
                if (!st.empty())
                {
                    st.pop();
                }
            }
            else
            {
                while (!st.empty() and (prec(s[i]) <= prec(st.top())))
                {
                    res += st.top();
                    st.pop();
                }
                st.push(s[i]);
            }
        }
        while (!st.empty())
        {
            res += st.top();
            st.pop();
        }
        return res;
    }
};

//{ Driver Code Starts.
// Driver program to test above functions
int main()
{
    int t;
    cin >> t;
    cin.ignore(INT_MAX, '\n');
    while (t--)
    {
        string exp;
        cin >> exp;
        Solution ob;
        cout << ob.infixToPostfix(exp) << endl;
    }
    return 0;
}

// } Driver Code Ends