PismenZad1

#include <iostream>
#include <stack>
#include <queue>

using namespace std;

int evaluate(queue<char> expr);

int main()
{
    queue<char> expression;
    string input;
    cout << "Enter expression: ";
    cin >> input;
    for (int i = 0; i < input.size(); i++)
    {
        expression.push(input[i]);
    }
    cout << "Result = " << evaluate(expression) << endl;
    return 0;
}

int evaluate(queue<char> expr)
{
    stack<int> nums;
    stack<char> funcs;

    while (!expr.empty())
    {
        char sym = expr.front();
        expr.pop();
        if (sym == 'f' || sym == 'g')
        {
            funcs.push(sym);
        }
        else if (sym >= '0' && sym <= '9')
        {
            nums.push(sym - '0');
        }
        else if (sym == ')')
        {
            int result = 0;
            int x = nums.top();
            nums.pop();
            if (funcs.top() == 'f')
            {
                result = (x*x + 3*x + 7) % 10;
            }
            else if (funcs.top() == 'g')
            {
                result = (3*x*x + 2*x + 4) % 10;
            }
            funcs.pop();
            nums.push(result);
        }
    }
    return nums.top();
}