How to remove duplicates from array using only a prefix of the values?

Question

my response is ["9s 0.4", "Jh 0.9", "8d 0.8", "8d 0.6", "5d 0.9", "3h 0.7", "9s 0.3", "2c 0.9", "As 0.7"]

Values are considered equal if they start with the same first 2 characters.

I want to remove the same value. ( ex: 8d display twice I want only single 8d)

@Prasann Welcome to SO. Note that this is not a code writing service. Please edit your question, post what you have tried and the issues you are facing. — Leo Dabus, Aug 10 '19 at 11:55
Your 8d's have different values next to them. What is the criteria for choosing one over the other? — vacawama, Aug 10 '19 at 11:56
func uniq(source: S) -> [T] { var buffer = [T]() var added = Set() for elem in source { if !added.contains(elem) { buffer.append(elem) added.insert(elem) } } return buffer } let vals = [1, 4, 2, 2, 6, 24, 15, 2, 60, 15, 6] let uniqueVals = uniq(vals) // [1, 4, 2, 6, 24, 15, 60] — Rebai Ahmed, Aug 10 '19 at 11:56
check this anwer :https://stackoverflow.com/questions/25738817/removing-duplicate-elements-from-an-array-in-swift — Rebai Ahmed, Aug 10 '19 at 11:56

vacawama · Accepted Answer · 2019-08-10T15:54:14.623

You are matching your array items by their prefix (first 2 letters). This is a little more complicated than the usual situation of handling duplicate values.

Here is a straightforward approach that uses a Set to keep track of the prefixes that have been seen while building the result array:

let arr = ["9s 0.4", "Jh 0.9", "8d 0.8", "8d 0.6", "5d 0.9", "3h 0.7", "9s 0.3", "2c 0.9", "As 0.7"]

// keep track of the prefixes we have seen
var prefixes = Set<String>()

// array to hold the results
var result = [String]()

for value in arr {
    // get the prefix for this value
    let prefix = String(value.prefix(2))

    // is this a new prefix?
    if !prefixes.contains(prefix) {
        // new prefix, so add value to new array
        result.append(value)

        // add prefix to our set
        prefixes.insert(prefix)
    }
}

print(result)

["9s 0.4", "Jh 0.9", "8d 0.8", "5d 0.9", "3h 0.7", "2c 0.9", "As 0.7"]

Functional Approach: Use filter with Set .inserted

(As @LeoDabus demonstated in this answer, you can use a Set with filter to remove custom duplicates)

You can do this with a functional approach which works in very much the same way as the approach shown above. It uses a Set to keep track of the prefixes seen and .inserted to decide if a new prefix was added to the Set. In the cases where a new prefix was added to prefixes, filter selects the item to be in the new results array.

let arr = ["9s 0.4", "Jh 0.9", "8d 0.8", "8d 0.6", "5d 0.9", "3h 0.7", "9s 0.3", "2c 0.9", "As 0.7"]

var prefixes = Set<Substring>()
let result = arr.filter { prefixes.insert($0.prefix(2)).inserted }
print(result)

["9s 0.4", "Jh 0.9", "8d 0.8", "5d 0.9", "3h 0.7", "2c 0.9", "As 0.7"]

`var set = Set()` `let filtered = arr.filter {set.insert($0.prefix(2)).inserted}` — Leo Dabus, Aug 10 '19 at 15:20
@LeoDabus, that is really slick. Please post that as answer. — vacawama, Aug 10 '19 at 15:30
https://stackoverflow.com/a/34712330/2303865 Done already. Works with String as well if you extend `RangeReplaceableCollection` and return `Self` — Leo Dabus, Aug 10 '19 at 15:32

How to remove duplicates from array using only a prefix of the values?

1 Answers1