Infix to Postfix

[hockey34]

A little lost. Program is not working properly and I'm sure there are a lot of errors. Please help.

#include <iostream>
#include <string>
using std::cout;
using std::cin;
using std::endl;
using std::string;

char InfixToPostfix(char infix[]);

struct node{
    char value;
    struct node *link;
};

node *top;

class stackAlgo{
private:
    int counter;
public:
    node *pushStack(node*, char);
    node *popStack(node*);
    char copyTop(node*);
    void printStack(node*);
    stackAlgo()
    {
        top = nullptr;
        counter = 0;
    }

};

node *stackAlgo::pushStack(node *top, char item)
{
    node *temp;
    temp = new (struct node);
    temp -> value = item;
    temp -> link = top;
    top = temp;
    counter++;
    return top;
}

node *stackAlgo::popStack(node *top)
{
    char item;
    node *temp;
    if (top == nullptr)
    {
        cout << "Stack is empty.";
    }
    else
    {
        temp = top;
        item = temp -> value;
        cout << item;
        top = top -> link;
        delete temp;
        counter--;
    }
    return top;
}

char stackAlgo::copyTop(node *top)
{
    char item;
    if (top == nullptr)
    {
        cout << "Stack is empty.";
    }
    else
    {
        item = top -> value;
    }
    return item;
}

void stackAlgo::printStack(node *top)
{
    node *ptr;
    ptr = top;
    if (top == nullptr)
    {
        cout << "Stack is empty.";
    }
    else
    {
        cout << "Stack elements: " << endl;
        while (ptr != nullptr)
        {
            cout << ptr -> value << endl;
            ptr = ptr -> link;
        }
    }
}

class InfixToPostfix{
public:
    InfixToPostfix() {}
    bool isOperand(char);
    bool isOperator(char);
    int weightOfOperator(char);
    char precedence(char, char);
    char output(char[]);
};

bool InfixToPostfix::isOperand(char a)
{
    bool flag = false;
    if (a >= 'a' && a <= 'Z')
    {
        flag = true;
        return flag;
    }
    else if (a >= 'A' && a <= 'Z')
    {
        flag = true;
        return flag;
    }
    else
        return flag;
}

bool InfixToPostfix::isOperator(char a)
{
    bool flag = false;
    if (a == '+')
    {
        flag = true;
        return flag;
    }
    else if (a == '-')
    {
        flag = true;
        return flag;
    }
    else if (a == '*')
    {
        flag = true;
        return flag;
    }
    else if (a == '/')
    {
        flag = true;
        return flag;
    }
    else
        return flag;

}

int InfixToPostfix::weightOfOperator(char a)
{
    int weight;
    if (a == '+' || a == '-')
    {
        weight = 1;
    }
    else if (a == '*' || a == '/')
    {
        weight = 2;
    }
    else if (a == '^')
    {
        weight = 3;
    }
    else
        weight = -1;
    return weight;
}

char InfixToPostfix::precedence(char a, char b)
{
    if (weightOfOperator(a) > weightOfOperator(b))
    {
        return a;
    }
    else
        return b;
}

char InfixToPostfix::output(char infix[])
{
    stackAlgo s;
    char result[11];
    int length = 11;
    char blank = NULL;
    for (int i = 0; i < length - 1; i++)
    {
        if (infix[i] == 'A' || infix[i] == 'B' || infix[i] == 'C' || infix[i] == 'D' || infix[i] == 'E')
        {
            result[i] = result[i] + infix[i];
        }
        else
        {
            while (top == nullptr && precedence(s.copyTop(top), infix[i]))
            {
                result[i] = result[i] + s.copyTop(top);
                s.popStack(top);
            }
            s.pushStack(top, infix[i]);
        }
        while (top == nullptr)
        {
            result[i] = result[i] + s.copyTop(top);
            s.popStack(top);
        }
    }
    for (int i = 0; i < 11; i++)
    {
        return result[i];
    }
    return blank;
}


int main()
{
    char infix1[11]; //Initalize and declare first infix pattern
    for (int i = 0; i < 11; i++)
    {
        cout << "Enter a character: ";
        cin >> infix1[i];
    }
    
    class InfixToPostfix object;
    
    char postfix = object.output(infix1);
    
    cout << postfix;

    
    return 0;
}