26.-remove-duplicates-from-sorted-array.md

26. Remove Duplicates from Sorted Array

Problem

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 * 10⁴
• -100 <= nums[i] <= 100
• nums is sorted in non-decreasing order.

PHP

Result

Runtime: 16 ms, Beats 94.62% of users with PHP

Memory: 21.04 MB, Beats 52.27% of users with PHP

class Solution
{
    /**
     * @param  int[]  $nums
     */
    public function removeDuplicates(array &$nums): int
    {
        $left = 0;

        for ($right = 1; $right < count($nums); $right++) {
            if ($nums[$left] !== $nums[$right]) {
                $nums[++$left] = $nums[$right];
            }
        }

        return $left + 1;
    }
}

Go

Result

Runtime: 0 ms, Beats 100.00% of users with Go

Memory: 4.47 MB, Beats 79.58% of users with Go

func removeDuplicates(nums []int) int {
	left := 0

	for right := 1; right < len(nums); right++ {
		if nums[left] != nums[right] {
			left++
			nums[left] = nums[right]
		}
	}

	return left + 1
}

Python

Result

Runtime: 67 ms, Beats 92.69% of users with Python3.

Memory: 18.02 MB, Beats 30.11% of users with Python3.

class Solution:
    def removeDuplicates(self, nums: List[int]) -> int:
        left = 0

        for right in range(1, len(nums)):
            if nums[left] != nums[right]:
                left += 1
                nums[left] = nums[right]

        return left + 1

TypeScript

Result

Runtime: 54 ms, Beats 97.22% of users with TypeScript

Memory: 53.12 MB, Beats 38.58% of users with TypeScript

const removeDuplicates = (nums: number[]): number => {
  let left: number = 0

  for (let right: number = 1; right < nums.length; right++) {
    if (nums[left] !== nums[right]) {
      nums[++left] = nums[right]
    }
  }

  return left + 1
}

JavaScript

Result

Runtime: 59 ms, Beats 80.13% of users with JavaScript

Memory: 51.76 MB, Beats 80.74% of users with JavaScript

/**
 * @param {number[]} nums
 * @return {number}
 */
const removeDuplicates = (nums) => {
  let left = 0

  for (let right = 1; right < nums.length; right++) {
    if (nums[left] !== nums[right]) {
      nums[++left] = nums[right]
    }
  }

  return left + 1
}

C#

Result

Runtime: 0 ms, Beats 100.00% of users with C#

Memory: 49.97 MB, Beats 64.76% of users with C#

public class Solution
{
    public int RemoveDuplicates(int[] nums) {
        int left = 0;

        for (int right = 1; right < nums.Length; right++)
        {
            if (nums[left] == nums[right])
                continue;

            left++;
            nums[left] = nums[right];
        }

        return left + 1;
    }
}