80. Remove Duplicates from Sorted Array II

https://leetcode.com/problems/remove-duplicates-from-sorted-array-ii/

JavaScript

/**
 * @param {number[]} nums
 * @return {number}
 */
var removeDuplicates = function(nums) {
  if (!nums || !nums.length) {
    return 0
  }

  var first = 0
  var second = 0

  for (let i = 1; i < nums.length; i++) {
    if (nums[i] !== nums[second]) {
      nums[++second] = nums[i]
      first = second
    } else if (first === second) {
      nums[++second] = nums[i]
    }
  }

  return second + 1
}

Python

class Solution(object):

    def removeDuplicates(self, nums):
        """
        :type nums: List[int]
        :rtype: int
        """
        if not nums:
            return 0
        first = second = 0
        for num in nums[1:]:
            if num != nums[second]:
                second += 1
                first = second
                nums[second] = num
            elif first == second:
                second += 1
                nums[second] = num
        return second + 1