如何在Swift中从字面上获得数组的相等大小切片

Question

例如，对于数组let array = [1, 3, -5, 2, 6]，我想获得此输出：数组切片的大小（N）相等。

如果N = 2，则输出：[1,3] [3,-5] [-5,2] [2,6]

如果N = 3，则输出：[1,3,-5] [3,-5,2] [-5,2,6]

/ / /更新我的代码，如下所示，winSize用于定义切片数组的大小，该大小来自readLine（）

class windowSize {
    var resultArray = [Int]()

    func execTest() {
        print("please give the window size W and length(S) of array, seperated by space")
        if let firstLine = readLine() {
            let firstLineArray = firstLine.compactMap{Int(String($0))}
            let winSize = firstLineArray[0]

            print("please give the test array with S length")
            if let arr1 = readLine() {
                let arr = arr1.compactMap{Int(String($0))}
                // print(arr)

                // get each slice array with window size length
                let slicedArray = arr.neighbors

                // get max value in each slice array
                for ele in slicedArray {
                    let max = ele.max()
                    resultArray.append(max!)
                }

                print("resultarray", resultArray)
            }
        }
    }
}

extension Collection {
    var neighbors: [SubSequence] {
        guard !isEmpty else { return [] }
        return indices.dropLast().map {
            return self[$0..<(index($0, offsetBy: 2, limitedBy: self.endIndex) ?? self.endIndex)]
        }
    }
}

windowSize().execTest()

Answer 1

这是一个简单的解决方案：

func windows<T>(in a: [T], ofSize w: Int) -> [[T]] {
    //You could decide here what you want to return if w is invalid
    if w > a.count || w <= 0 {
        return []
    }

    var output = [[T]]()
    for i in 0..<a.count-w+1 {
        output.append(Array(a[i..<i+w]))
    }
    return output
}

这是一些用例：

windows(in: [1, 3, -5, 2, 6], ofSize: 2) //[[1, 3], [3, -5], [-5, 2], [2, 6]]
windows(in: [1, 3, -5, 2, 6], ofSize: 3) //[[1, 3, -5], [3, -5, 2], [-5, 2, 6]]

Answer 2

您可以迭代删除最后一个的集合索引，并返回每个元素及其后续的邻居：

extension Collection {
    var neighbors: [SubSequence] {
        indices.dropLast().map {
            self[$0..<(index($0, offsetBy: 2, limitedBy: self.endIndex) ?? self.endIndex)]
        }
    }
}

---

let array = [1, 3, -5, 2, 6]
array.neighbors  // [[1, 3], [3, -5], [-5, 2], [2, 6]]

---

extension Collection {
    func customChunk(of n: Int) -> [[Element]] {
        indices.dropLast(n-1).map {
            .init(self[$0..<(index($0, offsetBy: n, limitedBy: self.endIndex) ?? self.endIndex)])
        }
    }
}
let array = [1, 3, -5, 2, 6]
array.customChunk(of: 3)  //   [[1, 3, -5], [3, -5, 2], [-5, 2, 6]]