Contoh Algoritma Sekuensial

Karakteristik Algoritma Sekuensial

Visualisasi Algoritma Sekuensial

Contoh 1: Linear Search (Pencarian Sekuensial)

Linear search adalah algoritma pencarian paling sederhana yang memeriksa setiap elemen secara berurutan. Untuk memahami lebih dalam tentang algoritma pencarian dan sorting, mari lihat implementasinya.

def linear_search(arr, target):
    """
    Mencari elemen target dalam array secara sekuensial
    Time Complexity: O(n)
    Space Complexity: O(1)
    """
    # Step 1: Inisialisasi
    n = len(arr)
    comparisons = 0
    
    # Step 2: Iterasi sekuensial
    for i in range(n):
        comparisons += 1
        print(f"Checking index {i}: {arr[i]}")
        
        # Step 3: Bandingkan dengan target
        if arr[i] == target:
            print(f"Found at index {i} after {comparisons} comparisons")
            return i
    
    # Step 4: Tidak ditemukan
    print(f"Not found after {comparisons} comparisons")
    return -1

# Contoh penggunaan
data = [64, 34, 25, 12, 22, 11, 90]
target = 22

print("Array:", data)
print(f"Searching for: {target}")
result = linear_search(data, target)

if result != -1:
    print(f"Element found at index: {result}")
else:
    print("Element not found")

function linearSearchWithStats(arr, target) {
    const stats = {
        comparisons: 0,
        steps: [],
        found: false,
        index: -1
    };
    
    // Sequential processing
    for (let i = 0; i < arr.length; i++) {
        stats.comparisons++;
        stats.steps.push({
            step: i + 1,
            index: i,
            value: arr[i],
            match: arr[i] === target
        });
        
        if (arr[i] === target) {
            stats.found = true;
            stats.index = i;
            break;
        }
    }
    
    return stats;
}

// Contoh penggunaan
const data = [5, 2, 8, 12, 3];
const target = 8;

const result = linearSearchWithStats(data, target);
console.log("Search Statistics:", result);
console.log(`Found: ${result.found}, Index: ${result.index}`);

Contoh 2: Bubble Sort (Pengurutan Sekuensial)

Bubble sort adalah algoritma pengurutan yang bekerja dengan membandingkan elemen bersebelahan secara berulang. Ini adalah contoh sempurna dari implementasi algoritma sorting sederhana.

def bubble_sort_visual(arr):
    """
    Bubble sort dengan visualisasi proses
    Time Complexity: O(n²)
    Space Complexity: O(1)
    """
    n = len(arr)
    total_swaps = 0
    
    print("Initial array:", arr)
    print("-" * 50)
    
    # Outer loop untuk setiap pass
    for i in range(n):
        swapped = False
        print(f"Pass {i + 1}:")
        
        # Inner loop untuk perbandingan
        for j in range(0, n - i - 1):
            print(f"  Comparing {arr[j]} and {arr[j + 1]}")
            
            # Sequential comparison dan swap
            if arr[j] > arr[j + 1]:
                arr[j], arr[j + 1] = arr[j + 1], arr[j]
                swapped = True
                total_swaps += 1
                print(f"  Swapped! Array: {arr}")
            else:
                print(f"  No swap needed")
        
        print(f"  End of pass {i + 1}: {arr}")
        print()
        
        # Optimasi: jika tidak ada swap, array sudah terurut
        if not swapped:
            print("Array already sorted!")
            break
    
    print(f"Final sorted array: {arr}")
    print(f"Total swaps: {total_swaps}")
    return arr

# Contoh penggunaan
data = [64, 34, 25, 12, 22, 11, 90]
print("Bubble Sort Demonstration")
print("=" * 50)
sorted_data = bubble_sort_visual(data.copy())

Contoh 3: Sequential File Processing

Pemrosesan file secara sekuensial adalah aplikasi praktis algoritma sekuensial dalam pengolahan data besar.

def process_student_data(filename):
    """
    Memproses data siswa secara sekuensial
    """
    students = []
    total_score = 0
    count = 0
    
    # Simulasi data (dalam praktik, baca dari file)
    student_data = [
        "Alice,85,90,78",
        "Bob,92,88,95", 
        "Charlie,76,82,89",
        "Diana,94,91,87",
        "Eve,88,85,92"
    ]
    
    print("Processing student data sequentially...")
    print("-" * 50)
    
    # Sequential processing setiap baris
    for line_num, line in enumerate(student_data, 1):
        print(f"Processing line {line_num}: {line}")
        
        # Parse data
        parts = line.strip().split(',')
        name = parts[0]
        scores = [int(score) for score in parts[1:]]
        
        # Calculate average
        avg_score = sum(scores) / len(scores)
        
        # Determine grade
        if avg_score >= 90:
            grade = 'A'
        elif avg_score >= 80:
            grade = 'B'
        elif avg_score >= 70:
            grade = 'C'
        else:
            grade = 'D'
        
        # Store result
        student = {
            'name': name,
            'scores': scores,
            'average': avg_score,
            'grade': grade
        }
        students.append(student)
        
        total_score += avg_score
        count += 1
        
        print(f"  {name}: Average = {avg_score:.2f}, Grade = {grade}")
    
    # Calculate class statistics
    class_average = total_score / count if count > 0 else 0
    
    print("\n" + "=" * 50)
    print("PROCESSING COMPLETE")
    print("=" * 50)
    print(f"Total students processed: {count}")
    print(f"Class average: {class_average:.2f}")
    
    return students

# Contoh penggunaan
students = process_student_data("students.txt")

# Display summary
print("\nStudent Summary:")
for student in students:
    print(f"{student['name']}: {student['average']:.2f} ({student['grade']})")

Contoh 4: Sequential Validation Algorithm

Algoritma validasi sekuensial sangat berguna untuk memvalidasi data input step-by-step.

def validate_user_registration(user_data):
    """
    Validasi data registrasi user secara sekuensial
    """
    validation_steps = []
    errors = []
    
    print("Starting sequential validation...")
    print("-" * 40)
    
    # Step 1: Validate username
    print("Step 1: Validating username...")
    username = user_data.get('username', '')
    if len(username) < 3:
        errors.append("Username must be at least 3 characters")
        validation_steps.append({"step": 1, "field": "username", "status": "FAIL"})
    elif not username.isalnum():
        errors.append("Username must contain only letters and numbers")
        validation_steps.append({"step": 1, "field": "username", "status": "FAIL"})
    else:
        validation_steps.append({"step": 1, "field": "username", "status": "PASS"})
    print(f"  Username validation: {'PASS' if not any('Username' in e for e in errors) else 'FAIL'}")
    
    # Step 2: Validate email
    print("Step 2: Validating email...")
    email = user_data.get('email', '')
    if '@' not in email or '.' not in email:
        errors.append("Invalid email format")
        validation_steps.append({"step": 2, "field": "email", "status": "FAIL"})
    else:
        validation_steps.append({"step": 2, "field": "email", "status": "PASS"})
    print(f"  Email validation: {'PASS' if '@' in email and '.' in email else 'FAIL'}")
    
    # Step 3: Validate password
    print("Step 3: Validating password...")
    password = user_data.get('password', '')
    password_valid = True
    
    if len(password) < 8:
        errors.append("Password must be at least 8 characters")
        password_valid = False
    
    if not any(c.isupper() for c in password):
        errors.append("Password must contain at least one uppercase letter")
        password_valid = False
    
    if not any(c.isdigit() for c in password):
        errors.append("Password must contain at least one number")
        password_valid = False
    
    validation_steps.append({"step": 3, "field": "password", "status": "PASS" if password_valid else "FAIL"})
    print(f"  Password validation: {'PASS' if password_valid else 'FAIL'}")
    
    # Step 4: Validate age
    print("Step 4: Validating age...")
    age = user_data.get('age', 0)
    if age < 13 or age > 120:
        errors.append("Age must be between 13 and 120")
        validation_steps.append({"step": 4, "field": "age", "status": "FAIL"})
    else:
        validation_steps.append({"step": 4, "field": "age", "status": "PASS"})
    print(f"  Age validation: {'PASS' if 13 <= age <= 120 else 'FAIL'}")
    
    # Final result
    is_valid = len(errors) == 0
    
    print("\n" + "=" * 40)
    print("VALIDATION COMPLETE")
    print("=" * 40)
    print(f"Overall status: {'VALID' if is_valid else 'INVALID'}")
    
    if errors:
        print("Errors found:")
        for i, error in enumerate(errors, 1):
            print(f"  {i}. {error}")
    
    return {
        'valid': is_valid,
        'errors': errors,
        'steps': validation_steps
    }

# Contoh penggunaan
user_data = {
    'username': 'john123',
    'email': 'john@example.com',
    'password': 'MyPassword123',
    'age': 25
}

result = validate_user_registration(user_data)
print(f"\nRegistration {'approved' if result['valid'] else 'rejected'}")

Contoh 5: Sequential Mathematical Computation

Perhitungan matematis yang memerlukan urutan operasi tertentu adalah aplikasi klasik algoritma sekuensial.

def calculate_statistics_sequential(data):
    """
    Menghitung statistik deskriptif secara sekuensial
    """
    if not data:
        return None
    
    n = len(data)
    print(f"Calculating statistics for {n} data points...")
    print("Data:", data)
    print("-" * 50)
    
    # Step 1: Calculate sum
    print("Step 1: Calculating sum...")
    total = 0
    for i, value in enumerate(data):
        total += value
        print(f"  Adding {value}: running sum = {total}")
    print(f"Final sum: {total}")
    
    # Step 2: Calculate mean
    print("\nStep 2: Calculating mean...")
    mean = total / n
    print(f"Mean = {total} / {n} = {mean:.2f}")
    
    # Step 3: Calculate variance
    print("\nStep 3: Calculating variance...")
    variance_sum = 0
    for i, value in enumerate(data):
        diff = value - mean
        squared_diff = diff ** 2
        variance_sum += squared_diff
        print(f"  ({value} - {mean:.2f})² = {squared_diff:.2f}")
    
    variance = variance_sum / n
    print(f"Variance = {variance_sum:.2f} / {n} = {variance:.2f}")
    
    # Step 4: Calculate standard deviation
    print("\nStep 4: Calculating standard deviation...")
    std_dev = variance ** 0.5
    print(f"Standard deviation = √{variance:.2f} = {std_dev:.2f}")
    
    # Step 5: Find min and max
    print("\nStep 5: Finding min and max...")
    min_val = data[0]
    max_val = data[0]
    
    for value in data:
        if value < min_val: min_val = value print(f" New minimum: {min_val}") if value > max_val:
            max_val = value
            print(f"  New maximum: {max_val}")
    
    # Step 6: Calculate median
    print("\nStep 6: Calculating median...")
    sorted_data = sorted(data)
    print(f"Sorted data: {sorted_data}")
    
    if n % 2 == 0:
        median = (sorted_data[n//2 - 1] + sorted_data[n//2]) / 2
        print(f"Median = ({sorted_data[n//2 - 1]} + {sorted_data[n//2]}) / 2 = {median}")
    else:
        median = sorted_data[n//2]
        print(f"Median = {median}")
    
    # Results
    results = {
        'count': n,
        'sum': total,
        'mean': mean,
        'variance': variance,
        'std_dev': std_dev,
        'min': min_val,
        'max': max_val,
        'median': median,
        'range': max_val - min_val
    }
    
    print("\n" + "=" * 50)
    print("STATISTICS SUMMARY")
    print("=" * 50)
    for key, value in results.items():
        if isinstance(value, float):
            print(f"{key.capitalize()}: {value:.2f}")
        else:
            print(f"{key.capitalize()}: {value}")
    
    return results

# Contoh penggunaan
data = [85, 92, 78, 96, 88, 76, 94, 82, 90, 87]
stats = calculate_statistics_sequential(data)

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