Calculate the data received inside the recursive function - arrays

Question

The function outputs via print() all possible combinations of the characters "abc". (Depending on the specified length)
I need to calculate this amount. I only managed to output these combinations one by one through print(). I left a comment in the right place of the code.
func allLexicographicRecur (_ string: [String.Element], _ data: [String], _ last: Int, _ index: Int){
var length = string.count-1
var data = data
for i in 0...length {
data[index] = String(string[i])
if index == last {
print(data.joined()) // Displays a combination. It is necessary to somehow calculate.
}else{
allLexicographicRecur(string, data, last, index+1)
}
}
}
func allLexicographic(_ l: Int) {
var alphabet = "abc"
var data = Array(repeating: "", count: l)
var string = alphabet.sorted()
var counter = 0
allLexicographicRecur(string, data, l-1, 0)
}
allLexicographic(3)
The function must somehow return the number of these combinations.
I would be very grateful for the help!
I managed to count only this way (but most likely it is not the best way to do it):
var count = 0
func allLexicographicRecur (_ string: [String.Element], _ data: [String], _ last: Int, _ index: Int){
var length = string.count-1
var data = data
for i in 0...length {
data[index] = String(string[i])
if index == last {
print(data.joined()) // Displays a combination. It is necessary to somehow calculate.
count += 1
}else{
allLexicographicRecur(string, data, last, index+1)
}
}
}
func allLexicographic(_ l: Int) {
var alphabet = "abc"
var data = Array(repeating: "", count: l)
var string = alphabet.sorted()
var counter = 0
allLexicographicRecur(string, data, l-1, 0)
}
allLexicographic(3)
print(count)

Answer 1

You do not need a global variable. There are at least two other options. You can add an inout parameter to allLexicographicRecur to keep track of the count or you can have allLexicographicRecur return its count.
Here's your code using a return value:
func allLexicographicRecur(_ string: [String.Element], _ data: [String], _ last: Int, _ index: Int) -> Int {
let length = string.count - 1
var data = data
var count = 0
for i in 0...length {
data[index] = String(string[i])
if index == last {
print(data.joined()) // Displays a combination. It is necessary to somehow calculate.
count += 1
} else {
count += allLexicographicRecur(string, data, last, index + 1)
}
}
return count
}
func allLexicographic(_ l: Int) -> Int {
let alphabet = "abc"
let data = Array(repeating: "", count: l)
let string = alphabet.sorted()
return allLexicographicRecur(string, data, l - 1, 0)
}
print(allLexicographic(3))
Here's your code updated to use an inout parameter.
func allLexicographicRecur(_ string: [String.Element], _ data: [String], _ last: Int, _ index: Int, _ count: inout Int){
let length = string.count - 1
var data = data
for i in 0...length {
data[index] = String(string[i])
if index == last {
print(data.joined()) // Displays a combination. It is necessary to somehow calculate.
count += 1
} else {
allLexicographicRecur(string, data, last, index + 1, &count)
}
}
}
func allLexicographic(_ l: Int) -> Int {
let alphabet = "abc"
let data = Array(repeating: "", count: l)
let string = alphabet.sorted()
var counter = 0
allLexicographicRecur(string, data, l - 1, 0, &counter)
return counter
}
print(allLexicographic(3))

Answer 2

You can not mange the count without global variable because of recursive function. so the method you wrote in question is perfect as per the output you want to have.