LeetCode Find All Numbers Disappeared in an Array

最新推荐文章于 2020-01-29 08:33:35 发布

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本文介绍了一个算法问题：如何在一个包含1到n整数的数组中找出所有未出现的数字，数组大小为n，某些数字出现了两次，而其他数字只出现一次。文章提供了一种不使用额外空间且运行时间为O(n)的解决方案。

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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]

#coding=utf-8
class Solution(object):
    def findDisappearedNumbers(self, nums):
        """
        :type nums: list[int]
        :rtype: list[int]
        """
        n = len(nums)
        s = set(nums) #已出现的数字
        res = [i for i in xrange(1,n+1)]
        res = set(res)
        for i in s:
            res.remove(i)
        return list(res) # beats 92.6% 268ms