Find All Numbers Disappeared in an Array
Easy
Given an array of integers where 1 ≤ a[i] ≤ n (n = size of the array), some elements appear twice and others appear once. Find all the elements of [1, n] inclusive that do not appear in the array.
Example 1
Input
[ 4, 3, 2, 7, 8, 2, 3, 1 ]
Output
[ 5, 6 ]
Explanation. 5 and 6 do not appear in the input array.
Example 2
Input
[ 1, 1 ]
Output
[ 2 ]
Explanation. 2 does not appear in the input array.
Example 3
Input
[ 1, 2, 3, 4, 5 ]
Output
[]
Explanation. All numbers from 1 to 5 appear in the input array.
Follow-up: Can you do it without extra space and in O(n) runtime? You may assume the returned list does not count as extra space.
Constraints:
1. Length of the array is in the range `[1, 10000]`.\n2. The integers in the array are in the range `[1, n]`, where `n` is the array size.
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