[leetcode] 448. Find All Numbers Disappeared in an Array @ python

原题

Given an array of integers where 1 ≤ a[i] ≤ n (n = size of array), some elements appear twice and others appear once.

Find all the elements of [1, n] inclusive that do not appear in this array.

Could you do it without extra space and in O(n) runtime? You may assume the returned list does not count as extra space.

Example:

Input:
[4,3,2,7,8,2,3,1]

Output:
[5,6]

解法

集合. 构造从1到n的集合, 将nums转化为集合, 然后求两个集合的差集.
Time: O(1)
Space: O(1)

代码

class Solution(object):
    def findDisappearedNumbers(self, nums):
        """
        :type nums: List[int]
        :rtype: List[int]
        """
        res = set(range(1, len(nums)+1)) - set(nums)
        return list(res)