关键：分治思想
    函数 partition 难理解一些，多看下就好了

    1. const swap = (arr, i, j) => {
    2.       if (i === j) return; 
    3.     const temp = arr[i]
    4.     arr[i] = arr[j]
    5.     arr[j] = temp
    6. }
    8. // 获取 pivot 交换完后的 index
    9. // 关键函数 以 pivot 为锚点 左右分开。
    10. const partition = (arr, pivot, left, right) => {
    11.     const pivotVal = arr[pivot]
    12.     let startIndex = left
    13.     for (let i = left; i < right; i++) {
    14.         if (arr[i] < pivotVal) {
    15.             swap(arr, i, startIndex)
    16.             startIndex++
    17.         }
    18.     }
    19.     swap(arr, startIndex, pivot)
    20.     return startIndex
    21. }
    23. const quickSort = (arr, left, right) => {
    24.     if (left < right) {
    25.         // 取 最右侧 的元素作为 pivot
    26.         let pivot = right
    27.         let partitionIndex = partition(arr, pivot, left, right)
    28.         console.log('incccc', arr)
    29.         quickSort(arr, left, partitionIndex - 1 < left ? left : partitionIndex - 1)
    30.         quickSort(arr, partitionIndex + 1 > right ? right : partitionIndex + 1, right)
    31.     }
    33. }
    36. const testArr = []
    37. let i = 0
    38. while (i < 10) {
    39.     testArr.push(Math.floor(Math.random() * 1000))
    40.     i++
    41. }
    42. console.log('unsort', testArr)
    43. quickSort(testArr, 0, testArr.length - 1);
    45. // unsort (10) [969, 549, 624, 140, 753, 281, 442, 884, 35, 681]
    46. // incccc (10) [549, 624, 140, 281, 442, 35, 681, 884, 969, 753]
    47. // incccc (10) [35, 624, 140, 281, 442, 549, 681, 884, 969, 753]
    48. // incccc (10) [35, 140, 281, 442, 549, 624, 681, 884, 969, 753]
    49. // incccc (10) [35, 140, 281, 442, 549, 624, 681, 884, 969, 753]
    50. // incccc (10) [35, 140, 281, 442, 549, 624, 681, 884, 969, 753]
    51. // incccc (10) [35, 140, 281, 442, 549, 624, 681, 753, 969, 884]
    52. // incccc (10) [35, 140, 281, 442, 549, 624, 681, 753, 884, 969]