public int removeDuplicates(int[] nums){
 if(nums.length<2)
return nums.length;

int pre =1;
int cur = 2;

while(nums.length>cur){
  if(nums[cur]==nums[pre]&&nums[cur]==nums[pre-1]){
     cur++;
   }
else{
  pre++;
  nums[pre] = nums[cur];
  cur++;
  }
 }return pre+1;
}