在数组中查找连续的元素序列

Question

经过研究，我只找到了获取数组中不连续元素序列的方法。我想知道是否有一种有效的方法可以使用 Swift.

获取数组中所有连续的元素序列

示例：
对于 [1, 2, 3]，答案是

Answer 1

只需使用两个带有列表切片的循环来获取所有连续的子序列。

let arr = [1,2,3,4]

var res = [[Int]]()

for i in 0..<arr.count {
    for j in i..<arr.count {
        res.append(Array(arr[i...j]))
    }
}

print(res)
// [[1], [1, 2], [1, 2, 3], [1, 2, 3, 4], [2], [2, 3], [2, 3, 4], [3], [3, 4], [4]]

Answer 2

使用函数式方法，解决方案类似于：

let numbers = [1,2,3,4]
let contiguousSubsequences = numbers.indices.flatMap { lowerBound in
    numbers[lowerBound...].indices.map { numbers[lowerBound...[=10=]] }
}
contiguousSubsequences  // [[1], [1, 2], [1, 2, 3], [1, 2, 3, 4], [2], [2, 3], [2, 3, 4], [3], [3, 4], [4]]

您还可以制作一个通用的计算属性扩展集合协议，允许您将它用于任何类型的集合，包括字符串和子序列：

extension Collection {
    var contiguousSubsequences: [SubSequence] {
        indices.flatMap { lowerBound in
            self[lowerBound...].indices.map { self[lowerBound...[=11=]] }
        }
    }
}

用法：

let numbers = [1,2,3,4]
let contiguousSubsequences = numbers.contiguousSubsequences
contiguousSubsequences  // [[1], [1, 2], [1, 2, 3], [1, 2, 3, 4], [2], [2, 3], [2, 3, 4], [3], [3, 4], [4]]

let letters = "abcd"
let contiguousSubstrings = letters.contiguousSubsequences
contiguousSubstrings  // ["a", "ab", "abc", "abcd", "b", "bc", "bcd", "c", "cd", "d"]

在数组中查找连续的元素序列

Find contiguous sequence of elements in an array

algorithm

swift