Given an array of sorted numbers, remove all duplicates from it. You should not use any extra space; after removing the duplicates in-place return the new length of the array.

remove_duplicates.py

def remove_duplicates(arr):
  firstPointer = 1
  secondPointer = 1
  while secondPointer < len(arr):
    if arr[firstPointer - 1] != arr[secondPointer]:
      # Replace duplicate with non duplicate
      arr[firstPointer] = arr[secondPointer]
      firstPointer += 1
    secondPointer +=1
      
  return firstPointer


def main():
  print(remove_duplicates([2, 3, 3, 3, 6, 9, 9]))
  print(remove_duplicates([2, 2, 2, 11]))


main()