PrefixEval.cpp

#include <iostream>
using namespace std;
const int Size=30;

struct Stack {
    int arr[Size];
    int top = -1;
};

void push(Stack &stack, int value) {
    if(stack.top == Size-1) {
        cout << "Stack is full" << value << endl;
        return;
    }
    stack.arr[++stack.top]=value;
}

int pop(Stack &stack) {
    if(stack.top == -1) {
        cout<<"Stack empty!"<<endl;
        return -1;
    }
    return stack.arr[stack.top--];
}

void display(Stack &stack) {
    if(stack.top == -1) {
        cout << "Stack is empty."<<endl;
        return;
    }
    cout << "Stack elements From top to bottom:";
    for (int i = stack.top;i >= 0; i--) {
        cout<< stack.arr[i]<<" ";
    }
    cout<<endl;
}

void evaluateExp(Stack &stack,string exp){
    char c;
    int val1;
    int val2;
    int character;
    int res;
    for (int i = exp.length() - 1; i >= 0; i--)
    {
        c = exp[i];
        if (c >= '0' && c <= '9')
        {
            character = (int)c - 48;
            push(stack,character);
        }
        else{ 
            val1 = pop(stack);  //the second operand
            val2 = pop(stack);  //the first operand
            switch (c)
            {
            case '+':
                res = val1 + val2;
                push(stack,res);
                break;
            case '-':
                res = val1 - val2;
                push(stack,res);
                break;
            case '*':
                res = val1 * val2;
                push(stack,res);
                break;
            case '/':
                if (c == '/' && val2 == 0) {
                    cout << "Error: Division by zero" << endl;
                    return;
                }            
                res = val1 / val2;
                push(stack,res);
                break;
            case '%':
                if (c == '%' && val2 == 0) {
                    cout << "Error: Division by zero" << endl;
                    return;
                }  
                res = val1 % val2;
                push(stack,res);
                break;
            default:
                break;
            }
        }
        display(stack);
    }
}
int main(int argc, char const *argv[])
{
    Stack stack; 
    string exp;
    cout<<"Enter the prefix expression: ";
    getline(cin,exp);
    evaluateExp(stack,exp);
    display(stack);
    return 0;
}