#include <iostream>
#include <stack>
#include <string>
using namespace std;
int performOperation(int operand1, int operand2, char operation)
{
switch (operation) {
case '+':
return operand1 + operand2;
case '-':
return operand1 - operand2;
case '*':
return operand1 * operand2;
case '/':
return operand1 / operand2;
default:
return 0;
}
}
// Function to evaluate the postfix expression
int evaluatePostfixExpression( string& expression)
{
stack<int> stack;
// for (int i = 0; i < expression.length(); i++)
for (int i = expression.length() - 1; i >= 0; --i)
{
char c = expression[i];
// Check if the character is a digit isdigit 0-9
if (isdigit(c)) {
// Convert char digit to int and push onto the stack
stack.push(c - '0');
// c is digit and ‘0’ ascii value is 48 , ‘1’ ascii value is 49
//49-48=1
} else {
// Pop the top two elements for the operation
int operand2 = stack.top();
stack.pop();
int operand1 = stack.top();
stack.pop();
// Perform the operation and push the result back onto the stack
int result = performOperation(operand1, operand2, c);
stack.push(result);
}
}
// The final result should be the only item left in the stack
return stack.top();
}
int main()
{
string expression2;
// the user for input
cout << "Enter a postfix expression";
cin>>expression2;
int result = evaluatePostfixExpression(expression2);
cout << "Result of Postfix Expression" <<result;
return 0;
}
