SOLVED: How to filter array according to set content?

@bitigchi

Sep '22

Looks basic, but I can't figure it out.

var array = [1, 2, 3, 4, 5, 6, 7]
var filteredArray: [Int] = []

var set = Set<Int>()
set.insert(1)
set.insert(2)
set.insert(3)
set.insert(4)

for s in set {
    filteredArray = array.filter { $0 == s }
}

print(filteredArray)

Expected outcome:

[1, 2, 3, 4]

Actual outcome:

// Single random number [4]

@Greenamberred HWS+

Sep '22

First of all, a Set is defined as an unordered collection of unique elements, which means there is no specified sequence order. If you wish to apply a sort order then you have to do that yourself, external to the Set.

var array = [1, 2, 3, 4, 5, 6, 7]
var filteredArray: [Int] = []

// var set = Set<Int>()
// set.insert(1)
// set.insert(2)
// set.insert(3)
// set.insert(4)

let set: Set = [4, 1, 3, 2]   // order does not matter as Set is an unordered collection of elements

for s in set {
    filteredArray.append(contentsOf: array.filter { $0 == s } )
}

print(filteredArray)  // will print effectively in a random order, as Set is unordered.
print(filteredArray.sorted())

@bitigchi

Sep '22

@Greenamberred, thanks! Got the logic now!

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