Simple Calculator with Operator Detection

🔑 Key Concepts

• Character Comparison: Using == to compare characters for operator detection
• Multiple Input Types: Reading integer, character, and integer in sequence
• Else-if Ladder: Testing multiple conditions for different operators
• Long Long Data Type: Handling large numbers up to 10^9
• Integer Division: Division of integers gives quotient, not decimal result
• Modulo Operator: Finding remainder using % operator
• Calculator Logic: Foundation for building more complex calculators

⚠️ Common Mistakes to Avoid

• Single vs Double Quotes: Use '+' (single quotes) for characters, not "+" (double quotes for strings)
• Uninitialized Variable: ans should be assigned in all cases, or use else for invalid operator
• Division by Zero: No check for b == 0 when dividing - could cause runtime error
• Input Order: Must read in correct order: number, operator, number (with spaces)
• Data Type Mismatch: Using int instead of long long may cause overflow for large numbers
• Wrong Operator Order: Checking division first is fine, but be consistent with logic

💡 Alternative: Switch Statement

This problem is perfect for demonstrating switch statement, which is cleaner for character-based decisions:

switch (ch) {
    case '+':
        ans = a + b;
        break;
    case '-':
        ans = a - b;
        break;
    case '*':
        ans = a * b;
        break;
    case '/':
        ans = a / b;
        break;
    case '%':
        ans = a % b;
        break;
    default:
        cout << "Invalid operator";
}

• Advantages: More readable, faster for many cases, clearly shows discrete choices
• When to use: Checking equality against multiple constant values (like operators)
• Don't forget: break statements prevent fall-through to next case

🎯 What You'll Learn

• How to compare characters using equality operator
• Reading mixed data types in a single input line
• Implementing basic calculator logic with conditionals
• Understanding integer division vs modulo operation
• When to use else-if vs switch for character matching
• Handling multiple arithmetic operations dynamically
• Real-world application: Building calculator programs

🚀 Enhancement Ideas

• Input Validation: Check if operator is valid before performing calculation
• Division by Zero: Add check: if (b == 0 && (ch == '/' || ch == '%'))
• Floating Point: Use double for decimal division results
• Multiple Operations: Allow chaining operations like "5 + 3 * 2"
• Error Messages: Print helpful error for invalid operators or division by zero