(leetcode 문제 풀이) Remove Element

Given an integer array nums and an integer val, remove all occurrences of val in nums in-place. The relative order of the elements may be changed.
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.

Custom Judge:
The judge will test your solution with the following code:

If all assertions pass, then your solution will be accepted.

Example 1:
Input: nums = [3,2,2,3], val = 3
Output: 2, nums = [2,2,_,_]
Explanation: Your function should return k = 2, with the first two elements of nums being 2. It does not matter what you leave beyond the returned k (hence they are underscores).

Example 2:
Input: nums = [0,1,2,2,3,0,4,2], val = 2
Output: 5, nums = [0,1,4,0,3,_,_,_]
Explanation: Your function should return k = 5, with the first five elements of nums containing 0, 0, 1, 3, and 4. Note that the five elements can be returned in any order. It does not matter what you leave beyond the returned k (hence they are underscores).
 
Constraints:
- 0 <= nums.length <= 100
- 0 <= nums[i] <= 50
- 0 <= val <= 100

# 투-포인터 알고리즘 사용
class Solution:
    def removeElement(self, nums: List[int], val: int) -> int:
        i = 0
        for j in range(len(nums)):
            if nums[j] != val:
                nums[i] = nums[j]
                i += 1
        return i

이전에 풀었던 (leetcode 문제 풀이) Remove Duplicates from Sorted Array (tistory.com) 문제와 거의 비슷했다. 실제로 해결한 방식도 투-포인터 알고리즘으로 동일했기 때문에 별 어려움은 없었다.

아래는 파이썬의 내장 함수인 count() 를 사용하여 nums 안에 val이 몇 개 들어있는지 조사한 뒤, remove() 를 통해 하나씩 지워가는 로직이다. for문을 사용해 제거해가면 인덱스 문제가 발생하기 때문에 while문을 사용했다.

# 파이썬 내장 함수 count 사용 
class Solution:
    def removeElement(self, nums: List[int], val: int) -> int:
        while nums.count(val):
            nums.remove(val)
        return len(nums)