题解 | #排序#

public int[] MySort (int[] arr) {
        // write code here
        int len = arr.length;
        quickSort(arr,0,len-1);
        return arr;
    }
    private void quickSort(int[] nums,int left,int right){
        if(left>=right){
            return;
        }
        int pivot = nums[left];
        //循环不变量
        //[left,low)<pivot
        //[low,i)=pivot
        //[high,right]>pivot
        int low = left;
        int high = right+1;
        int i = left;
        while(i<high){
            if(nums[i]<pivot){
                low++;
                swap(nums,i,low);
                i++;
            }else if(nums[i] == pivot){
                i++;
            }else{
                high--;
                swap(nums,i,high);
            }
        }
        swap(nums,left,low);
        quickSort(nums,left,low-1);
        quickSort(nums,low+1,right);
    }
    private void swap(int[] nums,int i,int j){
        int temp = nums[i];
        nums[i] = nums[j];
        nums[j] = temp;
    }