infix to prefix

#include <iostream>
#include<ctype.h>
using namespace std;
#define Max 20
int priority(char ch);
class InfixToPostfix
{

};
class Stack{
    char stack[Max];

    public:
    int top = 0;
    void push(char value)
    {
        if(top == Max-1)
        {
        cout<<"Stack Overflow"<<"\n";
        return;
        }
        top++;
        stack[top] = value;

    }
    char pop()
    {
        if(top == -1)
        {
            cout<<"Stack Underflow"<<"\n";
            return -1;
        }
        char value  = stack[top];
        top--;
        return value;
    }
    char peek()
    {
        return stack[top];
    }
};
int priority(char ch)
{
    if(ch=='^') return 3;
    if(ch == '*' || ch =='%' || ch == '/' ) return 2;
    if(ch == '+' || ch == '-') return 1;
    return 0;
}
int main() {
    char infix[] = "((A+B)*(C-D))+(F-G)";
    // for(int i=0;i<10;i++)
    // cout<<infix[i];
    char reverseinfix[20];
    for(int i=0;i<20;i++)
    {
        if(infix[19-i]==')'){
            reverseinfix[i] = '(';continue;}
        if(infix[19-i]=='('){
            reverseinfix[i] =')'; continue;}
        reverseinfix[i] = infix[19-i];
    }
    for(int i=0;i<20;i++)
        cout<<reverseinfix[i];
    cout<<"\n";
    char postfix[20];
    char prefix[20];
    int p_index = 0;
    Stack src;
    for(int i=0;i<20;i++)
    {
       if(reverseinfix[i]=='(') {
           src.push(reverseinfix[i]);
           continue;
       }

       if(reverseinfix[i]==')')
       {
           char ch = src.pop();
           while(ch != '(' && src.top!=-1)
           {
               postfix[p_index]= ch;
               p_index++;
               ch = src.pop();
           }
           continue;
       }

       if(reverseinfix[i]=='+'||reverseinfix[i]=='-'||reverseinfix[i]=='*'||reverseinfix[i]=='/'||reverseinfix[i]=='%'||reverseinfix[i]=='^')
       {
           if(src.top!=-1)
           {
               char op = src.pop();
               while(priority(op)>=priority(reverseinfix[i]) && src.top!=-1)
               {
                   postfix[p_index]= op;
                   p_index++;
                   op = src.pop();
               }
               src.push(op);
               src.push(reverseinfix[i]);
           }

           else
           {
           src.push(reverseinfix[i]);
           }

           continue;
       }

       if(isdigit(reverseinfix[i]) || isalpha(reverseinfix[i])){
             postfix[p_index]= reverseinfix[i];
             p_index++;
             continue;
       }
      }
      while(src.top!=-1)
      {
          char ch = src.pop();
          postfix[p_index] = ch;
          p_index++;
      }
      for(int i=0;i<p_index;i++)
      {
          prefix[i] = postfix[p_index-i];
      }
      for(int i=0;i<p_index;i++)
      {
          cout<<prefix[i];
      }
    return 0;
}