快速排序算法

public class QuickSort {

    private void sort(int[] arr, int start, int end){
        if (start < end) {
            int k = partion(arr, start, end);
            sort(arr, start, k - 1);
            sort(arr, k+1, end);
        }
    }

    private int partion(int[] arr ,int start, int end){
        int pivot = arr[start];
        while (start < end){
            while (start<end  && arr[end] >= pivot){
                end --;
            }
            arr[start] = arr[end];
            while (start<end && arr[start] <= pivot){
                start++;
            }
            arr[end] = arr[start];
        }
        arr[start] = pivot;
        return start;
    }

    private void topK(int[] arr, int k){
        int x = partion(arr,0,arr.length-1);
        while (x != k-1){
            if (x > k-1){
                x = partion(arr,0,x-1);
            }else {
                x = partion(arr,x+1,arr.length-1);
            }
        }
        for (int i = 0; i < k; ++ i){
            System.out.print(arr[i] + ",");
        }
    }

    public static void main(String[] args) {
        int[] arr = new int[100];
        for (int i = 0; i < 100; i++) {
            arr[i] = (int)(Math.random()*100+1);
            System.out.print(arr[i]+",");
        }
        System.out.println();
        QuickSort quickSort = new QuickSort();
        quickSort.sort(arr,0 ,arr.length-1);
        for (int i : arr) {
            System.out.print(i+",");
        }
        System.out.println();
        quickSort.topK(arr,10);
    }
}