private int[] removeDuplicates(int[] nums) {
        Arrays.sort(nums); 
        //index控制结果
        int index = 0;
        //i用来遍历每个数
        for (int i = 0; i < nums.length; i++) {
            if (nums[i] != nums[index]) {
                nums[++index] = nums[i];
            }
        }
        int[] result = new int[index + 1];
        for (int i = 0; i <= index; i++) {
            result[i] = nums[i];
        }
        return result;
    }