class Solution:
  def remove(self, arr):
    # TODO: Write your code here
    # non_dup_ptr to track non duplicate values
    # another is to scan our current value array
    # two cases: non duplicate and duplicate
    # non duplicate: not equal and it next to each other, increment non_duplicate
    # duplicate: keep increment duplicate until find no duplicate, increa non-duplicate and replace it value
    if len(arr) < 2:
      return 1
    non_dup_ptr = 0
    curr_ptr = 1 
    while curr_ptr < len(arr):
      if arr[non_dup_ptr] != arr[curr_ptr]:
        if curr_ptr > non_dup_ptr + 1: # we need to swap
          non_dup_ptr += 1
          arr[non_dup_ptr] = arr[curr_ptr]
        else:
          non_dup_ptr += 1
      curr_ptr += 1
      
    return non_dup_ptr + 1