0026. Remove Duplicates from Sorted Array.js

// Given a sorted array nums, remove the duplicates in-place such that each element appear only once and return the new length.
//
// Do not allocate extra space for another array, you must do this by modifying the input array in-place with O(1) extra memory.
//
// Example 1:
//
//   Given nums = [1,1,2],
//
//   Your function should return length = 2, with the first two elements of nums being 1 and 2 respectively.
//
//   It doesn't matter what you leave beyond the returned length.
//
// Example 2:
//
//   Given nums = [0,0,1,1,1,2,2,3,3,4],
//
//   Your function should return length = 5, with the first five elements of nums being modified to 0, 1, 2, 3, and 4 respectively.
//
//   It doesn't matter what values are set beyond the returned length.
//
// Clarification:
//
//   Confused why the returned value is an integer but your answer is an array?
//
//   Note that the input array is passed in by reference, which means modification to the input array will be known to the caller as well.
//
//   Internally you can think of this:
//
//     // nums is passed in by reference. (i.e., without making a copy)
//     int len = removeDuplicates(nums);
//
//     // any modification to nums in your function would be known by the caller.
//     // using the length returned by your function, it prints the first len elements.
//     for (int i = 0; i < len; i++) {
//       print(nums[i]);
//     }

/**
 * @param {number[]} nums
 * @return {number}
 */

/** Two pointers slow and fast */
// Time O(n)
// Space O(1)
const removeDuplicates = (nums) => {
  let slow = 0;
  let fast = 1;

  while (fast < nums.length) {
    if (nums[slow] !== nums[fast]) {
      slow++;
      nums[slow] = nums[fast];
    }
    fast++;
  }
  return slow + 1;
};