Remove Duplicates from Sorted Array

Nov 7, 2019 by Chris Luedtke

Description

Given a sorted array nums, remove the duplicates in-place such that each element appears only once, and return the new length.

Do not allocate extra space for another array.

# example
nums = [1, 2, 2, 3, 6, 7, 7]
unq_nums_len = remove_duplicates(nums)

print(unq_nums_len, nums, sep='/n')

>>> 5
    [1, 2, 3, 6, 7]

Solution

def remove_duplicates(nums: List[int]) -> int:
  if len(nums)==0:
    return 0

  i = 0
  for j in range(len(nums)):
    if nums[j] != nums[i]:
      # copy the new value to the pos in front of i
      # and increment both
      i += 1
      nums[i] = nums[j]
    # else i stays the same, increment j
  return i + 1