JAVA(快慢指針)

class Solution {
    public int removeDuplicates(int[] nums) {
        if (nums.length == 0) return 0;
        int i = 0;
        for (int j = 1; j<nums.length; j++){
            if (nums[j]!=nums[i]){
                i++;
                nums[i] = nums[j];
            }
        }
        
    }
    return i+1;
}

python

class Solution:
    def removeDuplicates(self, nums: List[int]) -> int:
        l = len(nums)
        i = 0
        while i<l-1:
            if nums[i+1]==nums[i]:
                del nums[i+1]
                l -= 1
            else:
                i += 1
        return l