Swift: Swiftの配列チュートリアル：作成、CRUD、走査メソッドの解説

// Alice's original "manual" approach
var cartItem1 = "Laptop"
var cartItem2 = "Mouse"
var cartItemPrice1 = 999.0
var cartItemPrice2 = 25.0
// By the time items piled up, she was lost...

var cartItems = ["Laptop", "Mouse", "Keyboard"]
var cartPrices = [999.0, 25.0, 89.0]
cartItems.append("Monitor")
cartPrices.append(349.0)
cartItems.remove(at: 1)
cartPrices.remove(at: 1)
print("Cart: \(cartItems)")
print("Total: $\(cartPrices.reduce(0, +))")

// Method 1: literal
let numbers = [1, 2, 3, 4, 5]
// Method 2: empty array
var emptyArray: [String] = []
// Method 3: repeated value
let zeros = Array(repeating: 0, count: 3)
print(zeros)
// Method 4: from range
let rangeArray = Array(10...15)
print(rangeArray)

let items = ["Apple", "Banana", "Orange"]
print("Count: \(items.count)")
print("Is empty: \(items.isEmpty)")
print("First: \(items.first ?? "None")")
print("Last: \(items.last ?? "None")")
print("Contains Apple: \(items.contains("Apple"))")

// ============================================
// Managing warehouse inventory with arrays
// ============================================
var inventory: [String] = []
if inventory.isEmpty {
    print("Warehouse is empty, adding stock...")
}
inventory.append("Laptop")
inventory.append("Mouse")
inventory.append("Keyboard")
inventory.append("Monitor")
print("Inventory has \(inventory.count) items")
print("Products: \(inventory.joined(separator: ", "))")
print("First item: \(inventory[0])")
print("Last item: \(inventory[inventory.count - 1])")

var tasks = ["Buy groceries", "Pay bills"]
// Append to end
tasks.append("Call doctor")
// Insert at specific position
tasks.insert("Check email", at: 0)
print(tasks)

var scores = [88, 92, 75, 60, 95]
// Modify
scores[1] = 98
// Remove
let removed = scores.remove(at: 3)
print("Removed: \(removed)")
scores.removeLast()
scores.sort()
print(scores)

// ============================================
// Simple to-do list with arrays
// ============================================
var todoList = ["Buy milk", "Walk dog", "Write report"]
// Add
todoList.append("Read book")
todoList.insert("Morning exercise", at: 0)
// Modify
todoList[2] = "Write weekly report"
// Remove
let completed = todoList.remove(at: 1)
print("Completed: \(completed)")
// Traverse
print("\n=== Today's Todo ===")
for (i, task) in todoList.enumerated() {
    print("\(i + 1). \(task)")
}
print("\nRemaining tasks: \(todoList.count)")

let numbers = [3, 7, 2, 8, 5, 1, 9, 4, 6]
// Basic for-in
for num in numbers {
    print(num, terminator: " ")
}
print()
// where filter
for num in numbers where num > 5 {
    print("\(num) is greater than 5")
}

let prices = [12.99, 24.50, 8.75, 35.00]
// map: add tax to each price
let withTax = prices.map { $0 * 1.08 }
print("With tax: \(withTax)")
// filter: items over 20
let expensive = prices.filter { $0 > 20 }
print("Expensive: \(expensive)")

// ============================================
// Analyzing order data with array operations
// ============================================
let orderAmounts = [45.0, 120.0, 33.5, 299.0, 55.0, 180.0, 22.0]
// 1. Total sales
let total = orderAmounts.reduce(0, +)
print("Total sales: $\(total)")
// 2. High-value orders (>= 100)
let highValue = orderAmounts.filter { $0 >= 100 }
print("High-value orders: \(highValue.count)")
// 3. Add 10% service fee to all orders
let withServiceFee = orderAmounts.map { $0 * 1.1 }
print("First 3 with fee: \(Array(withServiceFee.prefix(3)))")
// 4. Sort
let sorted = orderAmounts.sorted(by: >)
print("Top 3: \(Array(sorted.prefix(3)))")

// ============================================
// Shopping cart management system
// Combining array CRUD, traversal, and higher-order functions
// ============================================
import Foundation
var cartItems: [String] = []
var cartPrices: [Double] = []
func addItem(name: String, price: Double) {
    cartItems.append(name)
    cartPrices.append(price)
    print("Added: \(name) - $\(price)")
}
func removeItem(at index: Int) {
    guard index >= 0 && index < cartItems.count else {
        print("Invalid index")
        return
    }
    let removed = cartItems.remove(at: index)
    cartPrices.remove(at: index)
    print("Removed: \(removed)")
}
func updateQuantity(name: String, newPrice: Double) {
    if let index = cartItems.firstIndex(of: name) {
        cartPrices[index] = newPrice
        print("Updated: \(name) -> $\(newPrice)")
    }
}
func checkout() {
    guard !cartItems.isEmpty else {
        print("Cart is empty")
        return
    }
    print("\n=== Shopping Cart ===")
    var total = 0.0
    for (i, item) in cartItems.enumerated() {
        let price = cartPrices[i]
        total += price
        print("\(i + 1). \(item) - $\(String(format: "%.2f", price))")
    }
    let tax = total * 0.08
    let grandTotal = total + tax
    print("---")
    print("Subtotal: $\(String(format: "%.2f", total))")
    print("Tax (8%): $\(String(format: "%.2f", tax))")
    print("Total: $\(String(format: "%.2f", grandTotal))")
    let expensiveItems = cartPrices.enumerated().filter { $0.element > 100 }
    if !expensiveItems.isEmpty {
        print("\nHigh-value items:")
        for (i, _) in expensiveItems {
            print("  - \(cartItems[i])")
        }
    }
}
addItem(name: "Laptop", price: 999.0)
addItem(name: "Mouse", price: 25.0)
addItem(name: "Keyboard", price: 89.0)
addItem(name: "Monitor", price: 349.0)
addItem(name: "USB Hub", price: 35.0)
removeItem(at: 4)
updateQuantity(name: "Mouse", newPrice: 22.5)
checkout()