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]

# @lc code=start
using LeetCode

function find_all_numbers_disappeared_in_an_array(arr::Vector{Int})
    return setdiff(eachindex(arr), arr)
end

# add your code here:
# @lc code=end

find_all_numbers_disappeared_in_an_array (generic function with 1 method)

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