Algorithms Quiz | SP Contest 3 | Question 10

// C++ function to evaluate a given postfix expression
int evaluatePostfix(char* exp)
{
    // Create a stack of capacity equal to expression size
    stack<int> st;
    int i;
 
    // Scan all characters one by one
    for (i = 0; exp[i]; ++i)
    {
        // If the scanned character is an operand (number here),
        // push it to the stack.
        // The isdigit() function is used to check if a particular 
        // character in the given input string is a digit or not.
        if (isdigit(exp[i]))
            st.push(exp[i]);	// Statement 1
 
        //  If the scanned character is an operator, pop two
        // elements from stack apply the operator
        else
        {
            int val1 = st.top();    // Statement 2
            st.pop();
            int val2 = st.top();
            st.pop();
            
            switch (exp[i])		// Statement 3			
            {
             case \'+\': st.push(val2 + val1); break;
             case \'-\': st.push(val2 - val1); break;
             case \'*\': st.push(val2 * val1); break;
             case \'/\': st.push(val2/val1);   break;
            }
        }
    }
    
    return st.top();
}