#include <iostream>
using namespace std;
int main() {
    // Rectangle 1
    int length1 = 5, width1 = 10;
    int area1 = length1 * width1;
    cout << "Area 1: " << area1 << endl;

    // Rectangle 2 (Code must be rewritten/duplicated)
    int length2 = 3, width2 = 4;
    int area2 = length2 * width2;
    cout << "Area 2: " << area2 << endl;
return 0;
}

#include <iostream>
using namespace std;

// Function / Subroutine to calculate rectangle area
int calculateArea(int length, int width) {
    return length * width;
}

int main() {
    // Reusing the function cleanly
    cout << "Area 1: " << calculateArea(5, 10) << endl;
    cout << "Area 2: " << calculateArea(3, 4) << endl;
    return 0;
}

• Origin: Derived from German "Pfannkuchen" (pancake) — the act of flipping pancakes

• Algorithm: Given a permutation of N numbers, take the first element k, reverse the first k elements, repeat until the first element is 1

• Benchmark Goal: Generate all N! permutations (N=12 → 479,001,600 permutations), find the max flip count, maintain a checksum

• Why it's a great benchmark: Pure compute-bound (only integer ops + array manipulation, no I/O), highly parallelizable across CPU threads

• https://madnight.github.io/benchmarksgame/fannkuchredux-description.html#fannkuchredux

Initial: [4, 2, 1, 5, 3]

Step 0: [4, 2, 1, 5, 3]  → first=4 → flip first 4
Step 1: [5, 1, 2, 4, 3]  → first=5 → flip all 5
Step 2: [3, 4, 2, 1, 5]  → first=3 → flip first 3
Step 3: [2, 4, 3, 1, 5]  → first=2 → flip first 2
Step 4: [4, 2, 3, 1, 5]  → first=4 → flip first 4
Step 5: [1, 3, 2, 4, 5]  → first=1 → STOP!

Total Flips = 5

#include <iostream>
using namespace std;

int main() {
    cout << "Step 1: Program starting..." << endl;

    long long sum = 0;
    for (long long i = 1; i <= 100000000; i++) {
        sum += i;
    }

    cout << "Step 2: Sum calculated = " << sum << endl;
    return 0;
}

Syntax Error Behavior: If line 10 has a missing semicolon, the compiler halts immediately. No .exe is created. "Step 1" will NEVER print.

#include <iostream>
#include <string>
using namespace std;

int main() {
    string productName = "Bluetooth Headphones";
    int quantity = 2;
    double unitPrice = 450.0;

    double totalAmount = quantity * unitPrice;

    cout << "=== SALES INVOICE ===" << endl;
    cout << "Product: " << productName << endl;
    cout << "Total Amount: $" << totalAmount << endl;

    return 0;
}

• Name variables using camelCase (e.g., tenSanPham, tongTien)

• Use 4 spaces for indentation inside the main() function

• Add appropriate comments: // single-line comment or /* ... */ for multi-line

#include <iostream>
#include <iomanip>
using namespace std;

int main() {
    double score = 8.56789;
    double price = 12.50;

    // 1. Float with 2 decimal places
    cout << fixed << setprecision(2);
    cout << "Score: " << score << endl;
    // Output: 8.57

    // 2. Column alignment (setw)
    cout << left  << setw(15) << "Product"
         << right << setw(10) << "Price" << endl;
    cout << left  << setw(15) << "Bread"
         << right << setw(10) << price << endl;
    return 0;
}

• fixed: Display floating-point numbers in fixed decimal notation

• setprecision(n): Set n digits after the decimal point

• setw(w): Set minimum display width to w characters

• left / right: Align text left or right within the setw field

#include <string>
string s = "PTIT Academy";

// 1. String length
cout << s.length();    // 12

// 2. Check if empty
if (s.empty()) cout << "Empty!";

// 3. Concatenation
s += " Multimedia";

// 4. Character access
char c = s[0];          // 'P'

// 5. Extract substring
string sub = s.substr(0, 4); // "PTIT"

// 6. Find substring position
size_t pos = s.find("PTIT"); // 0

string name = " john DOE ";
string formatted = "";
bool isNewWord = true;

for (char c : name) {
 if (c != ' ') {
 if (isNewWord) {
 formatted += toupper(c);
 isNewWord = false;
 } else {
 formatted += tolower(c);
 }
 } else if (!isNewWord) {
 formatted += ' ';
 isNewWord = true;
 }
}
// Output: "John Doe"

Variable  Value     RAM Address
┌──────┬─────────┬────────────┐
│  x   │   42    │  0x1000    │ ◄──┐
├──────┼─────────┼────────────┤    │
│ ptr  │ 0x1000  │  0x2000    │ ───┘
└──────┴─────────┴────────────┘
(ptr holds value 0x1000 → Points to x)

Operations:
- ptr = &x  → ptr stores address 0x1000
- *ptr      → "Go to 0x1000, read value" → 42
- *ptr = 100 → "Go to 0x1000, write 100" → x = 100