class Solution {
public:
    int removeDuplicates(vector<int>& nums) {
        int n = nums.size();
        if (n == 0){
            return 0;
        }

        int fast = 1;
        int slow = 1;
        while (fast < n){
            if (nums[fast] != nums[fast - 1]){
                nums[slow] = nums[fast];
                slow++; 
            }
            fast++;
        }
        return slow;
    }
};