快排-分治法

public class QuickSortClass {
		
    public static void main(String[] args) throws Exception {
        int[] nums = {2,7,8,9,3,1,4,6,5};
        System.out.println(Arrays.toString(sort(nums)));
    }

    public static int[] sort(int[] sourceArray) throws Exception {
        int[] arr = Arrays.copyOf(sourceArray, sourceArray.length);
        return quickSort(arr, 0, arr.length - 1);
    }

    private static int[] quickSort(int[] arr, int left, int right) {
        if (left < right) {
            int partitionIndex = partition(arr, left, right);
            quickSort(arr, left, partitionIndex - 1);
            quickSort(arr, partitionIndex + 1, right);
        }
        return arr;
    }

    private static int partition(int[] arr, int left, int right) {
        // 设定基准值（pivot）
        int index = left + 1;
        for (int i = index; i <= right; i++) {
            if (arr[i] < arr[left]) {
                swap(arr, i, index);
                index++;
            }
        }
        swap(arr, left, index - 1);
        return index - 1;
    }

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

}