update,

marissa.sam/task2/temp/_draft/helloworld copy.cpp

@@ -0,0 +1,103 @@
+#include <iostream>
+#include <stack>
+#include <string>
+#include <cctype>
+#include <map>
+
+// Function to convert infix expression to postfix expression
+std::string infixToPostfix(const std::string &infix)
+{
+    std::stack<char> s;
+    std::string postfix;
+    std::map<char, int> precedence = {{'+', 1}, {'-', 1}, {'*', 2}, {'/', 2}, {'(', 0}};
+
+    for (char c : infix)
+    {
+        if (std::isalnum(c))
+        { // 1. if operand, add to postfix
+            postfix += c;
+        }
+        else if (c == '(')
+        { // 2. if '(', push to stack
+            s.push(c);
+        }
+        else if (c == ')')
+        { // 3. if ')', pop until '('
+            while (!s.empty() && s.top() != '(')
+            {
+                postfix += s.top();
+                s.pop();
+            }
+            if (!s.empty())
+                s.pop(); // pop '('
+        }
+        else
+        { // 4. if operator, pop operators with greater or equal precedence
+            while (!s.empty() && precedence[c] <= precedence[s.top()])
+            {
+                postfix += s.top();
+                s.pop();
+            }
+            s.push(c); // push current operator
+        }
+    }
+    // 5. pop remaining operators
+    while (!s.empty())
+    {
+        postfix += s.top();
+        s.pop();
+    }
+    return postfix;
+}
+
+// Function to evaluate postfix expression
+int evaluatePostfix(const std::string &postfix)
+{
+    std::stack<int> s;
+
+    for (char c : postfix)
+    {
+        if (std::isdigit(c))
+        { // 1. if operand, push to stack
+            s.push(c - '0');
+        }
+        else
+        { // 2. if operator, pop two operands, evaluate and push result
+            int op2 = s.top();
+            s.pop();
+            int op1 = s.top();
+            s.pop();
+            switch (c)
+            {
+            case '+':
+                s.push(op1 + op2);
+                break;
+            case '-':
+                s.push(op1 - op2);
+                break;
+            case '*':
+                s.push(op1 * op2);
+                break;
+            case '/':
+                s.push(op1 / op2);
+                break;
+            }
+        }
+    }
+    return s.top(); // 3. result is the only element in stack
+}
+
+int main()
+{
+    std::string infix;
+    std::cout << "Enter an arithmetic expression: ";
+    std::getline(std::cin, infix);
+
+    std::string postfix = infixToPostfix(infix);
+    std::cout << "Postfix expression: " << postfix << std::endl;
+
+    int result = evaluatePostfix(postfix);
+    std::cout << "Result: " << result << std::endl;
+
+    return 0;
+}