Implementing Quick Sort via Generics

QuickSort.swift

func quickSort<T: Comparable>(inout array: [T], var leftIndex: Int = 0, var rightIndex: Int = -1) {
        // O(n*log(n))
        if rightIndex == -1 { //we can call quickSort without start and end index in the beginning so first time we will assign last index of the array to the variable
            rightIndex = array.count - 1
        }
        
        var startLeftIndex = leftIndex
        var startRightIndex = rightIndex
        
        var pivot = array[leftIndex] //our pivot is the most left element
        
        while leftIndex < rightIndex {
            
            while array[rightIndex] >= pivot && leftIndex < rightIndex { //moving right if elements on the right are >= than the pivot
                
                rightIndex--
            }
            
            if leftIndex != rightIndex {
                
                array[leftIndex] = array[rightIndex] //switch elements bacause element on the left has to be less or equal than the pivot
                leftIndex++
            }
            
            
            
            while array[leftIndex] <= pivot && leftIndex < rightIndex {
                
                leftIndex++
            }
            
            if leftIndex != rightIndex {
                
                array[rightIndex] = array[leftIndex]
                rightIndex--
            }
        }
        
        array[leftIndex] = pivot//put pivot to the position where left index finished
        
        var pivotIndex = leftIndex
        leftIndex = startLeftIndex
        rightIndex = startRightIndex
        
        if leftIndex < pivotIndex {
            //recursive call
            self.quickSort(&array, leftIndex: leftIndex,  rightIndex: pivotIndex-1)
        }
        
        if rightIndex > pivotIndex {
            //recursive call
            self.quickSort(&array, leftIndex: pivotIndex + 1, rightIndex: rightIndex)
        }
    }
    
    /*  QUICK SORT TESTING  START */
        var testArray = ["s", "w", "i", "f", "t"]
        var myArray = [String]()
        myArray = testArray
        println("\(myArray) before sorting")
        quickSort(&myArray)
        println("\(myArray) after sorting")
        if sorted(myArray) == myArray {
            
            println("Quick Sort works")
        } else {
            
            println("QuickSort failed")
        }
        println("\n")
        /*  QUICK SORT TESTING END */