思路：

代码：

class Solution {
    public int removeDuplicates(int[] nums) {
        if(nums == null || nums.length == 0) return 0;
        int p = 0;
        int q = 1;
        while(q < nums.length){
            if(nums[q] != nums[p]){
                nums[p + 1] = nums[q];
                p++;
                q++;
            }else {
                q++;
            }
        }
        return p + 1;
    }
}