CODEWITHSUNDEEP
iosarraysswiftswift3
Shane
Shane

Reputation: 59

Swift 3 For loop compare and change

Here is my code so far

var counter = 0
    for i in 0...9 {
        var val = NamePicker()

        // array to find duplicates
        var buttonValues = ["", "", "", "", "", "", "", "", "", ""] // array for button names
        buttonValues.insert(val, at: counter)
        print(buttonValues[counter])
        counter += 1
    }

This code is putting 10 string values into my array. What I would like to do is find a way to check each value in my array. for eample if my end result array is ["a","a","a","b","b","c","c","e","f","c"] I want to see if there is a triple of the same name(single and duplicates are fine). However if there is a triple I would like to change the 3rd value to another val from my NamePicker() function.

so with my array of 

["a","a","a","b","b","c","c","e","f","c"]

there are 3 "a" and 3 "c", having two of the same is ok, i would like to change the 3rd to a new values and if the new value makes another triple it will change until there are no more triples.

so that array could possible have an end result of 

["a","a","f","b","b","c","c","e","f","z"]

this is where the triples where changed. Any help on how to do this efficiently?

Upvotes: 2

Views: 1813

Answers (3)

Yannick
Yannick

Reputation: 3278

Instead of inserting the wrong value and then checking if the values are correct, I would suggest to automatically create the correct array.

//array for button names
var buttonValues = Array<String>()
//tracks what value has been inserted how many times
var trackerDict = [String: Int]()
for i in 0...9 {

    //we initialize a new variable that tells us if we found a valid value (if the value has not been inserted 2 times already)
    var foundValidValue = false
    while !foundValidValue{
        var val = NamePicker()
        //now we check if the value exists and if it is inserted less than 2 times
        if let count = trackerDict[val] {
            if count < 2 {
                foundValidValue = true
            }
        }
        //if we found the value, we can add it
        if foundValidValue {
            trackerDict[val] = (trackerDict[val] ?? 0) + 1
            buttonValues.append(val)
        }
        //if we did not find it, we just run through the loop again
    }
}

I added a dictionary because it is faster to keep track of the count in a dictionary than counting the number of occurrences in the array every time.

Upvotes: 0

Code Different
Code Different

Reputation: 93181

Both options below asume that your NamePciker() function can generate at least 5 distinct values so there exists an array that satisfies your requirement.

Your requirement is better handled by not generating so many duplicates to begin with. If all you want is an array of names when each name cannot be repeated more than twice, try this:

var buttonValues = [String]()
var dict = [String: Int]()

while buttonValues.count < 10 {
    let name = NamePicker()
    let count = dict[name] ?? 0

    guard count < 2 else { continue }

    buttonValues.append(name)
    dict[name] = count + 1
}

If you already have the array and want to correct it, do this:

var buttonValues = ["a","a","a","b","b","c","c","e","f","c"]

// Scan the array to tally how many times each name appears
var totalDict = [String: Int]()
buttonValues.forEach { totalDict[$0] = (totalDict[$0] ?? 0) + 1 }

// Now scan it again to update names that appear too many times
var runningDict = [String: Int]()
for (index, value) in buttonValues.enumerated() {
    let count = runningDict[value] ?? 0

    if count >= 2 {
        while true {
            let newValue = NamePicker()
            let newTotal = (totalDict[newValue] ?? 0) + 1
            if newTotal < 3 {
                buttonValues[index] = newValue
                totalDict[newValue] = newTotal
                break
            }
        }
    } else {
        runningDict[value] = count + 1
    }
}

Upvotes: 1

Alex S
Alex S

Reputation: 582

Dictionary is the best way I think. Have the key be the character and the value be the count of that character. Your runtime will be O(n) since you only have to run through each input once. Here is an example:

let chars = ["a","a","a","b","b","c","c","e","f","c"]

var dict = [String: Int]()

for char in chars {
    //If already in Dictionary, increase by one
    if var count = dict[char] {
        count += 1
        dict[char] = count
    } else {//else is not in the dictionary already, init with 1
        dict[char] = 1
    }
}

Output:

["b": 2, "e": 1, "a": 3, "f": 1, "c": 3]

Now I'm not sure how you want to replace the value that's the same character for a third time, but this is probably the best way to group the strings to determine which are over the limit.

Upvotes: 0

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