CODEWITHSUNDEEP
arraysswift
user8549704
user8549704

Reputation:

Nested array andices for non nested array Swift

Heres something I'm trying to teach myself. I want a pair of elements in the nested indexArray to point to elements inside the numberArray:

IOW : IF indexArray has [[0,2],[3,4]] I want the nested elements to point towards element #0 and #2 in numberArray and elements 3 and 4 in numberArray

    func findNumIndex(numberArray: [Int], indexArray: [[Int]]) -> Int {
       // Use the NESTED index elements to arrive at element index in numberArrray
    }

    findNumIndex(nums: [0,1,2,3,4,5,6,7,8,9], queries: [[0,1],[1,2],[3,4]])

   // We would look at index 0 and 1, index 1 and 2, index 3 and 4 and get the numbers/

At first I thought about flattening the array, but that is NOT what I want.

Upvotes: 0

Views: 52

Answers (2)

Alexander
Alexander

Reputation: 63271

A bit over engineered, but this is a pretty handy extension that comes in a lot of circumstances:

extension RandomAccessCollection where Self.Index == Int {
    subscript<S: Sequence>(indices indices: S) -> [Self.Element]
        where S.Iterator.Element == Int {
        return indices.map{ self[$0] }
    }
}

let input = ["a", "b", "c", "d", "e"]
let queries = [[0, 1], [1, 2], [3, 4]]
let result = queries.map{ input[indices: $0] }

print(result) // => [["a", "b"], ["b", "c"], ["d", "e"]]

Upvotes: 0

Charles Srstka
Charles Srstka

Reputation: 17050

This seems like something you can do with a simple map:

indexArray.map { $0.map { numberArray[$0] } }

Upvotes: 2

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