infix to postfix conversion

1Best Solution
2-------------------------------------------------------------------
3#include<bits/stdc++.h>
4using namespace std;
5
6int prec(char c) {
7    if(c == '^') {
8        return 3;
9    }
10    else if(c == '*' || c == '/') {
11        return 2;
12    }
13    else if(c == '+' || c =='-') {
14        return 1;
15    }
16    else {
17        return -1;
18    }
19}
20
21string infixToPostfix(string s) {
22    stack<char> st;
23    string res;
24
25    for (int i = 0; i < s.length(); i++)
26    {
27        if((s[i] >= 'a' && s[i] <= 'z') || (s[i] >= 'A' && s[i] <= 'Z')) {
28            res += s[i];
29        }
30        else if(s[i] == '(') {
31            st.push(s[i]);
32        }
33        else if(s[i] == ')') {
34            while (!st.empty() && st.top() != '(')
35            {
36                res += st.top();
37                st.pop();
38            }
39            if(!st.empty()) {
40                st.pop(); // Popping '(' here
41            }
42        }
43        else {
44            while (!st.empty() && prec(st.top()) >= prec(s[i]))
45            {
46                res += st.top();
47                st.pop();
48            }
49            st.push(s[i]);
50        }
51    }
52    
53    while (!st.empty())
54    {
55       res += st.top();
56       st.pop();
57    }
58    
59    return res;
60}
61
62int main() {
63    string exp = "a+b*(c^d-e)^(f+g*h)-i";
64    cout<<infixToPostfix(exp);
65    return 0;
66}

1Begin
2   initially push some special character say # into the stack
3   for each character ch from infix expression, do
4      if ch is alphanumeric character, then
5         add ch to postfix expression
6      else if ch = opening parenthesis (, then
7         push ( into stack
8      else if ch = ^, then            //exponential operator of higher precedence
9         push ^ into the stack
10      else if ch = closing parenthesis ), then
11         while stack is not empty and stack top ≠ (,
12            do pop and add item from stack to postfix expression
13         done
14
15         pop ( also from the stack
16      else
17         while stack is not empty AND precedence of ch <= precedence of stack top element, do
18            pop and add into postfix expression
19         done
20
21         push the newly coming character.
22   done
23
24   while the stack contains some remaining characters, do
25      pop and add to the postfix expression
26   done
27   return postfix
28End