swift - Swift3 中的 Levenshtein 距离

Question

我正在使用来自 Rosetta Code 的教程计算 Levenshtein 距离。他们的代码似乎在 Swift2 中，所以我收到此错误 Binary operator '+' cannot be applied to operands of type '[Int]' and 'Repeated<String.CharacterView>'这样做时:var cur = [i + 2] + empty其中 let empty = repeatElement(s, count: 0) .我该怎么做？

Answer 1

需要进行一些更改。

• 构造空数组。
• enumerate() 现在是 enumerated()
• successor() 不再存在，所以我用 +1 替换了它

所以现在的功能是

swift 4:

func levDis(_ w1: String, _ w2: String) -> Int {
    let empty = [Int](repeating:0, count: w2.count)
    var last = [Int](0...w2.count)

    for (i, char1) in w1.enumerated() {
        var cur = [i + 1] + empty
        for (j, char2) in w2.enumerated() {
            cur[j + 1] = char1 == char2 ? last[j] : min(last[j], last[j + 1], cur[j]) + 1
        }
        last = cur
    }
    return last.last!
}

swift 3:

func levDis(w1: String, w2: String) -> Int {

    let (t, s) = (w1.characters, w2.characters)

    let empty = Array<Int>(repeating:0, count: s.count)
    var last = [Int](0...s.count)

    for (i, tLett) in t.enumerated() {
        var cur = [i + 1] + empty
        for (j, sLett) in s.enumerated() {
            cur[j + 1] = tLett == sLett ? last[j] : min(last[j], last[j + 1], cur[j])+1
        }
        last = cur
    }
    return last.last!
}