9、移除元素 leetcode27

描述

image.png

python方法：

class Solution:
    def removeDuplicates(self, nums: List[int]) -> int:
        flag = 0
        for i in range(len(nums)):
            if nums[i] != nums[flag]:
                flag += 1
                nums[i] = nums[flag]
        return flag+1

思路2: 交换，用指针start和last，当nums[start] == val 时交换到最后面，同时last-1，否则start+1

class Solution:
    def removeElement(self, nums: List[int], val: int) -> int:
        start, last = 0, len(nums)-1
        while start <= last:
            if nums[start]==val:
                nums[start],nums[last] = nums[last], nums[start]
                last = last - 1
            else:
                start = start + 1
                
        return last+1