# How to reverse an array using recursion ?

###### [Question] : Reverse array using recursion Example: [1,2,3] = [3,2,1]. Approach #1 using two variables : –
``````// Question reverse the string using recursion
// Here we are just swapping right with left & increase the left & right elements
func reverseArrayUsingRecursion(inArray: inout [Int],
rightElement: inout Int,
leftElement: inout Int) {

if rightElement >= leftElement {return}
inArray.swapAt(rightElement, leftElement)
rightElement += 1
leftElement -= 1
reverseArrayUsingRecursion(inArray: &inArray,
rightElement: &rightElement,
leftElement: &leftElement)
}

var inArray = [1, 2, 3, 4]
var rightElement = 0
var leftElement = inArray.count - 1
reverseArrayUsingRecursion(inArray: &inArray, rightElement: &rightElement, leftElement: &leftElement)
print(inArray) // prints [4, 3, 2, 1]``````
###### // Approach#2: Using single pointer/variable so we written base case which blocks on n/2, we are just increasing the element by +1 on every recursion till half of the array.
``````func reverseArrayUsingRecursion2(inArray: inout [Int],
startIndex: inout Int) {

if startIndex >= inArray.count/2 {return}
inArray.swapAt(startIndex, inArray.count-startIndex-1)
startIndex += 1
reverseArrayUsingRecursion2(inArray: &inArray,
startIndex: &startIndex)
}

var inArray2 = [1, 2, 3, 4]
var startIndex = 0
reverseArrayUsingRecursion2(inArray: &inArray2, startIndex: &startIndex)
print(inArray2)``````