reduce dan reduce(into:)

Apa Itu reduce?

Menjumlahkan dengan reduce

let nums = [1, 2, 3, 4]
let total = nums.reduce(0) { acc, x in acc + x }
print(total)  // 10

Singkatan Operator

let nums = [1, 2, 3, 4]
print(nums.reduce(0, +))   // 10
print(nums.reduce(1, *))   // 24

Mengurangi Menjadi Jenis Berbeda

let words = ["a", "b", "c"]
let joined = words.reduce("") { $0 + $1.uppercased() }
print(joined)  // "ABC"

Mencari Nilai Maksimum dengan reduce

let nums = [3, 9, 2, 7]
let maxVal = nums.reduce(Int.min) { max($0, $1) }
print(maxVal)  // 9

Biaya reduce

Memperkenalkan reduce(into:)

let nums = [1, 2, 2, 3, 3, 3]
let counts = nums.reduce(into: [Int: Int]()) { dict, n in
    dict[n, default: 0] += 1
}
print(counts)  // [1: 1, 2: 2, 3: 3]

Membangun Larik secara Efisien

let nums = [1, 2, 3, 4, 5]
let evensSquared = nums.reduce(into: [Int]()) { result, n in
    if n % 2 == 0 { result.append(n * n) }
}
print(evensSquared)  // [4, 16]

reduce dibandingkan reduce(into:)

let parts = ["a", "b", "c"]
let a = parts.reduce("") { $0 + $1 }            // copies each step
let b = parts.reduce(into: "") { $0 += $1 }    // mutates in place
print(a, b)  // abc abc

Mengelompokkan dengan reduce(into:)

let names = ["Ann", "Al", "Bo", "Cy"]
let byInitial = names.reduce(into: [Character: [String]]()) { dict, name in
    dict[name.first!, default: []].append(name)
}
print(byInitial[Character("A")]!)  // ["Ann", "Al"]

Memilih di Antara Keduanya

let nums = [1, 2, 3]
print(nums.reduce(0, +))                          // scalar: plain reduce
print(nums.reduce(into: Set<Int>()) { $0.insert($1) }) // collection: into

Pemeriksaan Singkat

Ringkasan