swift中的归并排序算法

func mergeSort(_ array: [Int]) -> [Int] {
    guard array.count > 1 else {
        return array
    }
    
    let middle = array.count / 2
    let leftArray = mergeSort(Array(array[0..<middle]))
    let rightArray = mergeSort(Array(array[middle..<array.count]))
    
    return merge(leftArray, rightArray)
}

func merge(_ leftArray: [Int], _ rightArray: [Int]) -> [Int] {
    var leftIndex = 0
    var rightIndex = 0
    var mergedArray: [Int] = []
    
    while leftIndex < leftArray.count && rightIndex < rightArray.count {
        if leftArray[leftIndex] < rightArray[rightIndex] {
            mergedArray.append(leftArray[leftIndex])
            leftIndex += 1
        } else {
            mergedArray.append(rightArray[rightIndex])
            rightIndex += 1
        }
    }
    
    while leftIndex < leftArray.count {
        mergedArray.append(leftArray[leftIndex])
        leftIndex += 1
    }
    
    while rightIndex < rightArray.count {
        mergedArray.append(rightArray[rightIndex])
        rightIndex += 1
    }
    
    return mergedArray
}

let array = [5, 2, 9, 1, 7, 6, 3]
let sortedArray = mergeSort(array)
print(sortedArray)  // 输出 [1, 2, 3, 5, 6, 7, 9]