CODEWITHSUNDEEP
arraysfindrangeswift4element
George
George

Reputation: 5

How to find number of elements of array in same range SWIFT

I will be happy with your help!

How can I find number of elements of array in same range? For example, var arrayOfInt = [1, 4, 9, 19, 38, 41] contains 3 elements of range 1...9, 1 element of range 10...19, 1 and 1 of ranges 30...39 and 40...49 respectively.

I need to count number of elements in each range (1...9, 10...19, 20...29, etc.). I suppose to use constant Dictionary with description of the ranges set, but to the end didn't understand how to solve that task.

Here is what I've got:

func finDRange(line: [Int]) -> [String: Int] {
        let sourceRange = ["R0": 1...9, "R1": 10...19, "R2": 20...29, "R3": 30...39, "R4": 40...49]
        var rangeDescription: [String: Int] = ["R0": 0, "R1": 0, "R2": 0, "R3": 0, "R4": 0]
        var count = 0
        for number in line {
        for (key, range) in sourceRange {
            if range.contains(number) {
                rangeDescription.updateValue(+1, forKey: key)
            }
            }
   }
        return rangeDescription
}

But it works correctly if only one number of array belongs to each range. That's where I stuck!

Upvotes: 0

Views: 208

Answers (1)

OOPer
OOPer

Reputation: 47886

I cannot be sure, but isn't this what you want to do?

func findRange(line: [Int]) -> [String: Int] {
    let sourceRange = ["R0": 1...9, "R1": 10...19, "R2": 20...29, "R3": 30...39, "R4": 40...49]
    var rangeDescription: [String: Int] = ["R0": 0, "R1": 0, "R2": 0, "R3": 0, "R4": 0]
    for number in line {
        for (key, range) in sourceRange {
            if range.contains(number) {
                rangeDescription[key] = (rangeDescription[key] ?? 0) + 1 //<- add 1 to the entry for the range
                break
            }
        }
    }
    return rangeDescription
}
var arrayOfInt = [1, 4, 9, 19, 38, 41]


let result = findRange(line: arrayOfInt)
print(result) //->["R0": 3, "R1": 1, "R2": 0, "R4": 1, "R3": 1]

As suggested by Leo Dabus, you can re-write the line: rangeDescription[key] = (rangeDescription[key] ?? 0) + 1 as:

rangeDescription[key] = rangeDescription[key, default: 0] + 1

This may be the preferred way when you want to supply default value for Dictionary access in Swift 4.

(I prefer using contains than ~=, but you can re-write it as in the comment of Leo Dabus.)

Upvotes: 1

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