基础快排

class Solution {
    public int[] sortArray(int[] nums) {
        quickSort(nums, 0, nums.length - 1);
        return nums;
    }

    private void quickSort(int[] nums, int left, int right) {
        if (left >= right) {
            return;
        }
        int partitionIndex = getPartitionIndex(nums, left, right);
        quickSort(nums, left, partitionIndex - 1);
        quickSort(nums, partitionIndex + 1, right);
    }

    private int getPartitionIndex(int[] nums, int left, int right) {
        int pivot = left;
        int index = pivot + 1;
        for (int i = index; i <= right; i++) {
            if (nums[i] < nums[pivot]) {
                swap(nums, i, index);
                index++;
            }
        }
        swap(nums, pivot, index - 1);
        return index - 1;
    }

    private void swap(int[] nums, int i, int j) {
        int temp = nums[i];
        nums[i] = nums[j];
        nums[j] = temp;
    }
}