How to find string B missing characters based on string A and add them to string B? - swift

Question

I have 2 strings.
var stringA = "LetDoItNow"
var stringB = "LetDo"
Is there a way that I can find characters that are not in string B based on string A and add them to string B in order that present in String A? If they are equal, no action needed.
stringA always contains all stringB characters in exact order of stringA.
Another example is
var stringA = “GoodMorning”
var stringB = “GoodM”
stringB will always follow stringA order but it could be missing some stringA characters. String B will never be something like this
var stringB = “Morning”
The missing characters in the 1st case are "ItNow" and my expected result after checking is
stringB = "LetDoItNow"
I hope to get missing characters so that i can run this code
stringB += “missingCharacters”
Thank you so much!

Answer 1

you can use stringA.components(separatedBy
var stringA = "LetDoItNow"
var stringB = "LetDo"
if stringA.count > stringB.count {
let component = stringA.components(separatedBy: stringB)
if component.count > 1{
stringB = stringB+component[1]
}
}
print(stringB)
You can Configure it better than this to make generic solution

Answer 2

Use a dictionary - store all characters and occurrences in String B, then compare String A and add what you are missing.
func letdoitnow() {
var dict = [Character:Int]()
for each in stringB {
dict[each] = (dict[each] ?? 0) + 1
}
for each in stringA {
dict[each] = (dict[each] ?? 0) - 1
if dict[each]! < 0 {
b += String(each)
}
}
}
This does not care about order though - unsure if that matters to you

Answer 3

If you want to add missing characters that are in stringA but not in stringB to StringB then you can use the following function:
private func addMissingCharacters(stringA: String, stringB: String) -> String {
if stringA == stringB {
return stringA
}
var result = stringB
for charachter in stringA {
if !stringB.contains(charachter) {
result.append(charachter)
}
}
return result
}
Here is a usage example:
let stringA = "LetDoItNow"
let stringB = "LetDo"
let result = addMissingCharacters(stringA: stringA, stringB: stringB)
print("Result: \(result)") // Will print: LetDoINw
As you can see, the result is "LetDoINw" not "LetDoItNow", because 't' of "It" and 'o' of "Now" are there in stringB so they won't be added again.