RemoveDuplicatesFromSortedArray.ts

// Source : https://leetcode.com/problems/remove-duplicates-from-sorted-array/
// Author : squxq
// Date   : 2023-09-08

/** ***************************************************************************************************
 *
 * Given an integer array nums sorted in non-decreasing order, remove the duplicates in-place such
 * that each unique element appears only once. The relative order of the elements should be kept the
 * same. Then return the number of unique elements in nums.
 *
 * Consider the number of unique elements of nums to be k, to get accepted, you need to do the
 * following things:
 *
 * 	Change the array nums such that the first k elements of nums contain the unique elements in
 * the order they were present in nums initially. The remaining elements of nums are not important as
 * well as the size of nums.
 * 	Return k.
 *
 * Custom Judge:
 *
 * The judge will test your solution with the following code:
 *
 * int[] nums = [...]; // Input array
 * int[] expectedNums = [...]; // The expected answer with correct length
 *
 * int k = removeDuplicates(nums); // Calls your implementation
 *
 * assert k == expectedNums.length;
 * for (int i = 0; i < k; i++) {
 *     assert nums[i] == expectedNums[i];
 * }
 *
 * If all assertions pass, then your solution will be accepted.
 *
 * Example 1:
 *
 * Input: nums = [1,1,2]
 * Output: 2, nums = [1,2,_]
 * Explanation: Your function should return k = 2, with the first two elements of nums being 1 and 2
 * respectively.
 * It does not matter what you leave beyond the returned k (hence they are underscores).
 *
 * Example 2:
 *
 * Input: nums = [0,0,1,1,1,2,2,3,3,4]
 * Output: 5, nums = [0,1,2,3,4,_,_,_,_,_]
 * Explanation: Your function should return k = 5, with the first five elements of nums being 0, 1, 2,
 * 3, and 4 respectively.
 * It does not matter what you leave beyond the returned k (hence they are underscores).
 *
 * Constraints:
 *
 * 	1 <= nums.length <= 3 * 10^4
 * 	-100 <= nums[i] <= 100
 * 	nums is sorted in non-decreasing order.
 ******************************************************************************************************/

export function removeDuplicates(nums: number[]): number {
  let k = 0;
  let indexNumber = 0;
  const uniqueNums = new Set();
  for (const num of nums) {
    if (uniqueNums.has(num)) {
      k++;
    } else {
      nums[indexNumber++] = num;
      uniqueNums.add(num);
    }
  }
  return nums.length - k;
}