leetcode刷题系列 448. Find All Numbers Disappeared in an Array

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]

Subscribe to see which companies asked this question

Show Tags

Show Similar Problems

Have you met this question in a real interview? 

Yes

class Solution {
public:
    vector<int> findDisappearedNumbers(vector<int>& nums) {
        int len = nums.size();
        vector<int> res;
        for(int i = 0; i < len; ++i)
        {
            if(nums[i] == i + 1)
                continue;
            else
            {
                while(nums[i] != i + 1 && nums[nums[i] - 1] != nums[i])
                {
                    int tmp = nums[i];
                    nums[i] = nums[tmp - 1];
                    nums[tmp - 1] = tmp;
                }
            }
        }
        
        for(int i = 0; i < len; ++i)
        {
            if(nums[i] != i + 1)
                res.push_back(i + 1);
        }
        return res;
    }
};

不停的做交换操作 直到每个位置跟该位置处的元素值一致为止。