Swift相当于Ruby的“each_cons”

ruby

Ruby有each_cons可以像这样使用

class Pair def initialize(left, right) @left = left @right = right end end votes = ["a", "b", "c", "d"] pairs = votes.each_cons(2).map { |vote| Pair.new(*vote) } p pairs # [#, #, #] 

迅速

swift中的代码相同，但没有each_cons函数

 struct Pair { let left: String let right: String } let votes = ["a", "b", "c", "d"] var pairs = [Pair]() for i in 1..<votes.count { let left = votes[i-1] let right = votes[i] pairs.append(Pair(left: left, right: right)) } print(pairs) // [Pair(left: "a", right: "b"), Pair(left: "b", right: "c"), Pair(left: "c", right: "d")] 

如何使这个快速代码更短或更简单？

Answer 1

 zip(votes, votes.dropFirst()) 

这会产生一系列元组。

例

 struct Pair { let left: String let right: String } let votes = ["a", "b", "c", "d"] let pairs = zip(votes, votes.dropFirst()).map { Pair(left: $0, right: $1) } print(pairs) // [Pair(left: "a", right: "b"), Pair(left: "b", right: "c"), Pair(left: "c", right: "d")] 

Answer 2

这是我提出的一般解决方案，但它看起来有点非常低效。 要实现each_cons(n) ，请将我的each_cons(n)设置为n ：

  let arr = [1,2,3,4,5,6,7,8] let clump = 2 let cons : [[Int]] = arr.reduce([[Int]]()) { memo, cur in var memo = memo if memo.count == 0 { return [[cur]] } if memo.count < arr.count - clump + 1 { memo.append([]) } return memo.map { if $0.count == clump { return $0 } var arr = $0 arr.append(cur) return arr } }