[Leetcode] 27. Remove Element

題目 : 27. Remove Element

Given an integer array nums and an integer val, remove all occurrences of val in nums in-place. The order of the elements may be changed. Then return the number of elements in nums which are not equal to val.

Consider the number of elements in nums which are not equal to val 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 elements which are not equal to val. The remaining elements of nums are not important as well as the size of nums.
• Return k.

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).

1.

雖然題目的文字很多，但是其實目的就只是要將nums中所有的val值進行刪除的動作。

如果這邊是使用if而不是while的話，就只會刪除第一個出現在nums的val值

class Solution:
    def removeElement(self, nums: List[int], val: int) -> int:
        
        # 將nums中的val值移除，直到nums沒有val的值出現
        while val in nums:
            nums.remove(val)
				 # 最後回傳nums剩下幾個元素
        return len(nums)