448. Find All Numbers Disappeared in an Array ->LetCode

最新推荐文章于 2020-01-29 08:33:35 发布

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干啥啥不行，吃饭第一名。吃饭不积极，脑子有问题。

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本文探讨了一种在不使用额外空间且运行时间为O(n)的情况下，找出数组中未出现的所有[1,n]范围内元素的方法。通过标记数组元素的出现状态，遍历后找到未被标记的元素即为所求。

Problem:

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]

https://leetcode.com/problems/find-all-numbers-disappeared-in-an-array/

class Solution {
public:
    vector<int> findDisappearedNumbers(vector<int>& nums) {
        
        int max = nums.size();
        vector<int> vec;
        max++;
        bool isAppeared[max] = {false};
        
        for (auto it = nums.begin(); it!= nums.end(); it++){
            isAppeared[*it] = true;
        }
        for (int i=1; i<max; i++){
            if (isAppeared[i] == false)
                vec.push_back(i);
        }
        
        return vec;
        
    }
};