LeetCode - 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]

建立一个大小为size + 1的哈希表，O（n）的时间填充哈希表，O（n）的时间扫描哈希表并添加元素。

class Solution {public:    vector<int> findDisappearedNumbers(vector<int>& nums) {        vector<int> vec;        int size = nums.size();        int* table = new int[size + 1] { 0 };                for( int i = 0; i < size; i++ ) {            table[nums[i]]++;        }                for( int i = 1; i <= size; i++ ) {            if( table[i] == 0 ) vec.push_back( i );        }                return vec;    }};