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.
Input: [4, 3, 2, 7, 8, 2, 3, 1]
Output: [5, 6]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.
Input: [4, 3, 2, 7, 8, 2, 3, 1]
Output: [5, 6]