原题出处：https://leetcode.cn/leetbook/read/top-interview-questions-easy/x2gy9m/

解法一：

public static int removeDuplicates(int[] nums) {
        int len = nums.length;
        int index = 0;
        for (int i = 0; i < len; i++) {
            if (nums[i] != nums[index]) {
                index++;
                nums[index] = nums[i];
            }
        }
        return index + 1;
    }