快速排序的两种写法研究

以首数字为分界点

private static int[] quick_sort(int[] unsorted) {
        int[] sorted = unsorted.clone();
        int left = 0;
        int right = sorted.length - 1;
        _quick_sort(sorted, left, right);
        return sorted;
    }

    private static void  _quick_sort(int[] sorted, int left, int right) {
        if (left >= right) {
            return;
        }
        int i = left;
        int j = right;
        int mid = sorted[left];
        while (i < j) {
            while (sorted[j] >= mid && i < j) {
                j--;
            }
            sorted[i] = sorted[j];
            while (sorted[i] <= mid && i < j) {
                i++;
            }
            sorted[j] = sorted[i];
        }
        sorted[i] = mid;
        _quick_sort(sorted, left, i - 1);
        _quick_sort(sorted, i + 1, right);
//        return sorted;
    }

以中间数为分界点

public static void main(String[] args) {
        int[] arr = ArrayUtil.getRandomArr(80000);
        log.info("排序前");
//        System.out.println(Arrays.toString(arr));
        int l = 0;
        int r = arr.length - 1;
        recursionSort(arr, l, r);
        log.info("排序后");
//        System.out.println(Arrays.toString(arr));
    }

    private static void recursionSort(int[] arr, int left, int right) {
        int l = left;
        int r = right;
        int pivot = arr[(left + right) / 2];
        int temp;
        while (l < r) {
            while (arr[l] < pivot) {
                l += 1;
            }
            while (arr[r] > pivot) {
                r -= 1;
            }

            if (l >= r) {
                break;
            }

            temp = arr[l];
            arr[l] = arr[r];
            arr[r] = temp;
            if (arr[l] == pivot) {
                r -= 1;
            }
            if (arr[r] == pivot) {
                l += 1;
            }
        }
        if (l == r) {
                l++;
                r--;
            }
//        log.info(Arrays.toString(arr));
        if (left < r) {
            recursionSort(arr, left, r);
        }
        if (right > l) {
            recursionSort(arr, l, right);
        }
    }