0080-remove-duplicates-from-sorted-array-ii.js

/**
 * 80. Remove Duplicates from Sorted Array II
 * https://leetcode.com/problems/remove-duplicates-from-sorted-array-ii/
 * Difficulty: Medium
 *
 * Given an integer array nums sorted in non-decreasing order, remove some duplicates in-place such
 * that each unique element appears at most twice. The relative order of the elements should be kept
 * the same.
 *
 * Since it is impossible to change the length of the array in some languages, you must instead have
 * the result be placed in the first part of the array nums. More formally, if there are k elements
 * after removing the duplicates, then the first k elements of nums should hold the final result.
 * It does not matter what you leave beyond the first k elements.
 *
 * Return k after placing the final result in the first k slots of nums.
 *
 * Do not allocate extra space for another array. You must do this by modifying the input array
 * in-place with O(1) extra memory.
 */

/**
 * @param {number[]} nums
 * @return {number}
 */
var removeDuplicates = function(nums) {
  let offset = 2;

  for (let i = 2; i < nums.length; i++) {
    if (nums[i] !== nums[offset - 2]) {
      nums[offset] = nums[i];
      offset++;
    }
  }

  return offset;
};