Recursive function with loops inside - swift

Question

I am trying to generalize loops within a recursive function...
The basic double loop is the following function:
func multiLoops(start ix:Int, upTo n:Int) {
for i in ix...n {
for j in i+1 ... n+1 {
print("it is \(i) \(j)")
}
}
}
multiLoops(start: 3, upTo: 6)
With the following result:
it is 3 4
it is 3 5
it is 3 6
it is 3 7
it is 4 5
it is 4 6
it is 4 7
it is 5 6
it is 5 7
it is 6 7
My tentative to do the same with a recursive function is the following:
func multiLoopsRecursive(start ix:Int, upTo n:Int, loopNumber:Int){
var loopNumber = loopNumber
var previous_i = ix
func loop(start ix:Int, upTo n:Int) {
for i in ix + 1...n {
print("it is \(previous_i) \(i)")
if loopNumber > 1 {
loopNumber -= 1
previous_i = i
loop(start: previous_i+1, upTo: n+loopNumber)
}
}
}
loop(start: ix, upTo: n)
}
multiLoopsRecursive(start: 3, upTo: 6, loopNumber: 2)
With the following result ...
it is 3 4
it is 4 6
it is 4 7
it is 4 5
it is 4 6
Not really the same as the basic double loop ...
I am really blocked...
Thank you for your help...
Regards
K

Answer 1

Basic double loop with a print loopNumber added:
for i in ix...n {
print("it is loop 1")
for j in i+1 ... n+1 {
print("it is loop 2")
print("it is \(i) \(j)")
}
}
}
multiLoops(start: 3, upTo: 6)
Result:
it is loop 1
it is loop 2
it is 3 4
it is loop 2
it is 3 5
it is loop 2
it is 3 6
it is loop 2
it is 3 7
it is loop 1
it is loop 2
it is 4 5
it is loop 2
it is 4 6
it is loop 2
it is 4 7
it is loop 1
it is loop 2
it is 5 6
it is loop 2
it is 5 7
it is loop 1
it is loop 2
it is 6 7
Larme, Please find your code with the loopNumber added:
var loopNumber = 1
func multiLoopsRecursive(start: Int, upTo: Int) {
print("it is loop \(loopNumber)")
for i in start+1...upTo+1 {
print("it is \(start) \(i)")
}
let newStart = start + 1
if newStart < upTo+1 {
loopNumber += 1
multiLoopsRecursive(start: newStart, upTo: upTo)
}
}
print("Recursive")
multiLoopsRecursive(start: 3, upTo: 6)
Result:
Recursive
it is loop 1
it is 3 4
it is 3 5
it is 3 6
it is 3 7
it is loop 2
it is 4 5
it is 4 6
it is 4 7
it is loop 3
it is 5 6
it is 5 7
it is loop 4
it is 6 7
Thank you for your support
K

Answer 2

Here we are !
The trick is to know in which loop you are to adapt the different variables. I leave in the code the « print loop down and up » for more clarity, but it can be suppressed of course.
Now it works with loops in loops :-)
func loopInLoop (iStart:Int, iEnd:Int, numberOfLoops : Int) {
print("what loop is it! \(loopIndex)")
var iRank = 0
for i in iStart...(iEnd - numberOfLoops + loopIndex) {
iArray[loopIndex-1] = i
iRank += 1
if loopIndex < numberOfLoops {
print ("loop down")
loopIndex += 1
loopInLoop(iStart: iStart + iRank, iEnd: iEnd, numberOfLoops: numberOfLoops)
} else {print("iArray:\(iArray)")}
}
print ("loop up")
loopIndex -= 1
}
let iStart = 3 // initial starting index of first loop, must be <= iEnd
let iEnd = 7 // ending starting index of first loop
let numberOfLoops = 2 // number of loop to execute, must be <= (iEnd-iStart)
var iArray = [Int](repeating: 0, count: numberOfLoops) // Array of indexes
var loopIndex = 1 // initial index of the loop
loopInLoop(iStart: iStart, iEnd: iEnd, numberOfLoops : numberOfLoops)
Result:
what loop is it! 1
loop down
what loop is it! 2
iArray:[3, 4]
iArray:[3, 5]
iArray:[3, 6]
iArray:[3, 7]
loop up
loop down
what loop is it! 2
iArray:[4, 5]
iArray:[4, 6]
iArray:[4, 7]
loop up
loop down
what loop is it! 2
iArray:[5, 6]
iArray:[5, 7]
loop up
loop down
what loop is it! 2
iArray:[6, 7]
loop up
loop up