https://leetcode.cn/problems/find-all-numbers-disappeared-in-an-array/ (opens new window) 需要注意的点

1. %n操作，是因为在原数组的基础上加上n，那么在计算该索引的时候就需要%n得到原来的数
2. set,setA - setB

class Solution:
    def findDisappearedNumbers(self, nums: List[int]) -> List[int]:
        n = len(nums)
        for num in nums:
            x = (num-1) %n
            nums[x] += n
        
        ret = [ i+1 for i, num in enumerate(nums) if num <= n]
        return ret

class Solution:
    def findDisappearedNumbers(self, nums: List[int]) -> List[int]:
        len_arr = len(nums) +1
        setA = set([i for i in range(1, len_arr)])
        setB = set(nums)

        return list(setA-setB)

class Solution:
    def findDisappearedNumbers(self, nums: List[int]) -> List[int]:

        len_arr = len(nums)
        index = 0
        while index < len_arr:

            if nums[index] == index+1:
                index += 1
            else:
                targetIndex = nums[index] -1
                if nums[targetIndex] == nums[index]:
                    index += 1
                    continue
                
                temp = nums[targetIndex]
                nums[targetIndex] =nums[index]
                nums[index] = temp
        l = []
        for index, v in enumerate(nums):
            if v != index +1:
                l.append(index+1)
        return l