Collections Practice

// PROJECT 1: Student Gradebook
var gradebook: [String: [Int]] = [
    "Alice": [95, 88, 92, 90],
    "Bob": [78, 85, 80, 88],
    "Charlie": [92, 95, 98, 94]
]

// Calculate average for each student
for (name, grades) in gradebook {
    let average = grades.reduce(0, +) / grades.count
    print("\(name): \(average)")
}

// Find the top student
let topStudent = gradebook.max { a, b in
    a.value.reduce(0, +) < b.value.reduce(0, +)
}
print("Top student: \(topStudent!.key)")

// PROJECT 2: Shopping Cart
var cart: [[String: Any]] = []

func addItem(name: String, price: Double, quantity: Int) {
    cart.append([
        "name": name,
        "price": price,
        "quantity": quantity
    ])
}

addItem(name: "Apple", price: 0.99, quantity: 5)
addItem(name: "Bread", price: 2.49, quantity: 2)
addItem(name: "Milk", price: 3.99, quantity: 1)

// Calculate total
var total = 0.0
for item in cart {
    if let price = item["price"] as? Double,
       let qty = item["quantity"] as? Int {
        total += price * Double(qty)
    }
}
print("Total: $\(String(format: "%.2f", total))")

// PROJECT 3: Word Frequency Counter
let text = "the quick brown fox jumps over the lazy dog"
let words = text.split(separator: " ")

var frequency: [String: Int] = [:]
for word in words {
    let w = String(word)
    frequency[w, default: 0] += 1
}

// Sort by frequency
let sorted = frequency.sorted { $0.value > $1.value }
for (word, count) in sorted {
    print("\(word): \(count)")
}

// PROJECT 4: Leaderboard
var scores: Set<Int> = [100, 85, 92, 78, 95, 88]

// Add new scores
scores.insert(99)
scores.insert(85)  // Already exists, ignored

// Get top 3
let top3 = Array(scores.sorted(by: >).prefix(3))
print("Top 3: \(top3)")  // [100, 99, 95]